Chapter 3 - The Pre-Natal Life Of The Dog

In the former chapter we left the ripe ova in the oviducts, or Fallopian tubes, of the bitch awaiting fertilization by the spermatozoa from the male dog. If the spermatozoa fail to ascend into the oviduct within a few days of the deposit of the ova, they lose their vigor and perish. (In the original edition of this book it is written that the sperm "pine and die of loneliness." A "pining" sperm would be a sight to see. P.O.) Let us assume, however, that the bitch has been mated to a dog of vigorous fertility and that we are ready to note what occurs.

The process of fertilization has been observed under the microscope and even photographed as it occurs between the gametes of lower forms of life. There is sufficient evidence that the process is the same in the higher animals to justify our assumption of what occurs at this stage in our friend, the dog.

We are not sure at the present level of knowledge what it is that once the sperm are deposited in the vagina attracts them to the ova. Whatever the attraction—a chemical field or an electrical field or both—one of the sperm will eventually reach the outer membrane of an ovum. At the touch of the sperm, a tiny bump rises on the ovum at the point of juncture and the sperm is seemingly’ sucked into the egg. Its journey is far from over, however, since it has yet to make its way through an inner membrane, across the area of cytoplasm , and through the nuclear membrane. It had been previously thought that the tail of the sperm, having served its function of propelling the sperm to the ovum, dropped off when the sperm-head penetrated the outer membrane. Quite recent evidence indicates that the tail does NOT drop off but, rather, remains intact to the point of nuclear penetration. We must bear in mind that the sperm must penetrate three membranes, as well as making its way across a relatively vast expanse of cytoplasm .

As soon as the sperm has penetrated the outer membrane an immediate chemical reaction takes place which hardens the outer membrane so that no further penetration of additional sperm is possible. Also, the sperm within the membrane cannot withdraw. When each ripe ovum in the tube has been penetrated by a single sperm, the remaining male gametes, being superfluous, perish. ("Superfluous" may be the wrong word since it is entirely possible that the remaining sperm act as nutriment for the developing embryo or serve to maintain a vital PH balance.)

Within the minute head of the sperm is the cell nucleus and within that tiny compass is compressed all of the sire's contribution to the development of the new organism.

Within the female ovum is a tiny, dark spot—the nucleus— which contains the hereditary contribution to the new organism from the dam and her ancestors. When the head of the sperm fuses with the nucleus of the ovum, fertilization has then, and only then, taken place. If the sperm should die between the outer and the inner membranes or between the inner membrane and the nuclear membrane, that ovum will not be fertilized.

The fusion of the two nuclei produces a single nucleus and from this nucleus will develop the dog that is, if not to see the light, for puppies are born with closed eyes, at least to breathe the air and conjure up our admiration and delight and wonder some nine weeks later.

In the dog each of the nuclei which unite to form the new nucleus contains the haploid number of chromosomes (39), which is just half of the diploid number (78). In fact every cell in the body of the dog contains the diploid number, except only the functional gametes after their meiotic reduction. The intensely interesting drama of the chromosomes and their genes is too involved for discussion at this point and will require a complete chapter in itself. Suffice it to say here that the new cell, formed by the union of the nuclei from the male and female cells, contains the full diploid number of chromosomes. This reference to the chromosomes should not be permitted to confuse the reader and may well be ignored until its significance is made clear.

The new cell formed by the union of the male and female gametes is technically known as a zygote (Greek, "yoked"). In mammals the zygote is also known in its early stages as an embryo and in its late stages as a fetus.

It may be useful to think of cells as the fundamental units of living matter, the bricks from which all living structures are built. Most individual cells are microscopically small, although there are many cells large enough to be visible to the naked eye and some are of considerable size, e.g., the yolk of a newly laid bird egg is a single cell.

We shall not here go into the details of cell structure, more than to say that the cell is made up of its nucleus, or central body, and its surrounding material known as the cytoplasm . All animal or vegetable growth is the result of the splitting and proliferation of cells. (See diagram on page 70.)

The nucleus of the zygote or fertilized ovum, now a single cell, begins to halve and separate, its parts drawing toward opposite poles. The spherical cytoplasm grows ovoid in shape, half of the original nucleus in each end of it. An indentation creeps around the equator of the cytoplasm and grows deeper. The two parts later are connected by a mere isthmus of cytoplasm and the isthmus finally disappears, making two cells of what has previously been one. Each of these new cells has its nucleus and its cytoplasm . These new cells are called daughter cells and each one of them has the full number, the diploid count, of chromosomes as had the original zygote, the chromosomes having split longitudinally to supply each daughter cell with its full complement. This miracle of the splitting of the cell is technically known as mitosis (see glossary) or cleavage.

Each of the daughter cells in its turn divides into two more cells in the same manner. They, now four, in their turn divide into eight, the eight into sixteen, and the organism develops more and more rapidly by the division of cells by geometric progression. There are soon hundreds, thousands, millions, billions of cells in a higher organism such as a dog.

As soon as the ovum is fertilized, the new zygote normally begins to move gradually down the oviduct toward its ultimate destination in the uterus. The progress is slow and the journey may require several days. Meanwhile, the cell division continues, but it is yet a slow process and the new organism is yet minute. The tiny yolk substance of the ovum forms the bulk of its nourishment and cleavage cannot proceed very far without food.

Occasionally an embryo settles down to develop in the oviduct and does not pass on toward the uterus. Such a condition, known as a tubal pregnancy, is abnormal, very rare, and equally dangerous to the mother. The tubal pregnancy must be surgically removed else the developing fetus will cause a rupture.

Normally, the developing organism reaches the uterus, but it is yet only a tiny mass of a few hundred cells. But the cells not only have continued to proliferate, they have begun to structure themselves in a preliminary but definite pattern to form the new organism. This process of the beginning of structure is the same for all higher animals from jellyfish to man. The similarity of this basic beginning reveals the essential unity of all life.

There is a potential design hidden in the chromosomes of the germ plasma which decrees the pattern the segmenting cells shall assume. A kind of chromo somatic blueprint in the zygote lays down a plan which determines that the developing organism, of which the parental gametes were from dogs, shall take the pattern of a dog. If the parental gametes were from giraffes, the pattern would be that of a giraffe; if a parrot, the pattern would be that of a parrot. And the blueprint not only describes a dog but also describes what kind of dog, Dachshund or Greyhound, Pekingese or Saint Bernard, and not only the breed but also the type within the breed. All the attributes, good or bad, desirable or hateful, which it is possible for the organism ever to possess, are innate in this unfolding design.

If this small mass of cells should die at such an inter-uterine stage, it is needless to say that the design would never be executed, and if the design were of a Collie it will never herd sheep, if a Pointer it will never hunt birds. And even if it lives, environmental influences may knock the design into a cocked hat. However excellent the design, insufficient or incorrect nourishment may produce rickets, or an amputated leg may make a cripple of the organism. But that would be no fault of the design.

The new puppy is a-forming. The other fertilized ova also have begun their segmentation and proliferation and have also descended into the uterus, each of the embryos developing after the design laid down in its zygotic chromosomes.

To follow this design, development by development, involves the use of a lot of technical nomenclature which would confuse more than it would clarify the subject for most readers. Suffice it to say that the cell mass is no longer apparently amorphous but has begun to grow into a puppy.

The walls of the small uterus are tough and thick. Menstruation has cleaned it out. Its lining has been broken up, washed away, and replaced by fresh and young tissue in anticipation of the embryos which have now arrived.

Arrived in the uterus, our embryo fastens itself to the prepared wall to spend a couple of months while it grows into a puppy and builds itself in accordance with the design and specifications set forth in its chromosomes. Warm and snug as it is in this dark chamber, which has been all house-cleaned and relined for its reception, yet it has nothing to eat. The tinier yolk in the tiny ovum has been consumed. The original zygotic cell has segmented into hundreds of cells, each complete with its nucleus and cytoplasm . Now if the cell mass is to continue to grow it must have nourishment from some source.

The embryo is a hollow mass of cells. Settling down in the uterus, it embeds itself into the uterine lining, eating its way into the walls and destroying some of the uterine cells. It digs in and is surrounded on all sides by the maternal tissue and laved with the maternal blood, which provides it with the nourishment of which it was in need. Now, with a food supply, the little parasite, for such it is, can grow and can continue its segmentation and development of its pattern. It should be understood that at no time does the blood of the mother mingle with the blood of the embryo, the two systems being completely separate throughout the entire pre-natal period. As we shall see, however, the nourishment for the embryo is filtered from the blood of the mother just as waste material from the embryo is filtered back to the blood of the mother.

None of the organs of the future puppy are yet detectable. The first noticeable growth is not of the puppy itself but rather of the elaborate membranes to enwrap the embryo and the ducts to feed it.

Indeed, the group of cells which implants itself in the uterus is not, properly speaking, the puppy itself but is one of these covering membranes, the chorion, within which the embryonic body is later to appear. During the early development, the embryo consists of three hollow vesicles, one inside the other.

On the wall which separates these two inner chambers appears a minute disk, and across it is a shallow groove, the so-called primitive streak. This is the first appearance of the puppy itself. The other part of the development so far detectable has been only of the apparatus for his growth and nurture. This disk, the new puppy, proliferates and develops very rapidly. In nine short weeks it is to be a dog, squeaking and whining and crawling about in search of its mother's teats.

The embryo is immersed in a solution called the amniotic fluid, which is contained in a membrane known as the amnion.

This liquid absorbs jars or blows which the maternal organism may receive and saves the developing embryo from discomfort. The amniotic fluid is germicidal and its bath prevents bacterial infection of the embryo. Later it is to prove of similar service to the membranes of the bitch while she whelps her brood.

Outside the amnion is another membrane known as the cho-rion. And over all is a layer of maternal tissue. So we see that our precious pup is triply housed and antiseptically bathed.

In the center of the ventral surface of the embryo is a small orifice known as the umbilicus (later to be known as the navel). From it a tube grows out which develops into the umbilical cord. At birth this cord appears attached to the belly of the puppy. The umbilical cord connects with and grows into a disk of tissue called the placenta, which is in intimate contact with the walls of the uterus. The placenta is the essential organ of nutrition, excretion, and respiration for the embryo. From the placenta by means of the umbilical cord, food and oxygen are filtered from the bloodstream of the mother to the fetus and waste products in gaseous form are eliminated to the placenta and thence back to the bloodstream of the mother.

The umbilical cord houses two arteries and a single large vein. The cord has no nerves and so the only communication between the mother and the fetus is by way of that complex filtration plant, the placenta. It is not possible for any nervous stimulus, favorable or unfavorable, to be transmitted to the offspring. Naturally, any factors which affect the nutrition of the mother will in turn have an affect upon the nutrition of the fetus .

Thus we see that the growing organism is as well protected as is naturally possible. Bathed with an antiseptic solution, swaddled in protecting membranes, kept at an even, warm temperature, fed through a tube to its belly, the fetus lives "a life of Riley"—nothing to do for nine weeks but to grow and grow and grow.

And grow it does. It seems as it develops that things have gone amiss, that the design being realized is most anything but a dog: first, a fish, then an amphibian, then a reptile, then a primitive mammal. All of the seemingly false starts can now be evaluated in the proper perspective. The embryo has re-enacted in nine brief weeks the entire evolutionary development of its race. A billion years of evolutionary history have been compressed unbelievably into nine weeks.

It would serve no purpose to follow in detail the various stages in the development of the fetus . But it is worthy of note that, since the placenta serves in lieu of lungs, intestines, and kidneys combined, the development of those organs can be postponed. But the puppy does need a heart very early and it is the first of the major organs to develop, begins to function in the worm-like embryo and keeps up its incessant beating until the dog, worn out with age, lies down and gives up the ghost. (Note: it should not be thought that the embryonic heart when it first appears is structurally complete. The first heart has only two chambers, as does that of the fish. The complete four-chambered mammalian heart, like the mammalian kidney, develops in the closing week of the dog's pre-natal life.)

Nature is zealous that the species shall not die. Very early in the development of the embryo some cells are set aside from the proliferation with which the puppy can reproduce his kind, if all goes well and if he can find a mate. These reproductive cells, the germ plasma , exist for one sole purpose, that the race may not die. Bathed and fed and cared for by the other, so called somatic, cells, they take no part in the growth or activity of the organism but lie in patient waiting until instinct prompts the adult animal to mate with another of the opposite sex, at which time they supply the material for the gametes which are to contribute to the new generation.

The chromosomes of the basic reproductive cells, i.e., before they split to become functional reproductive cells, are of the full number (the diploid count). The chromosomes are, in fact, exactly like those in all of the other cells of the body, as we shall see in Chapter V, "The Chromosomes and Their Genes."

It would be impossible, even if desirable, to state the size of the embryo at the various stages of its development since it must needs vary as the various breeds of dogs vary in their size.

Growth is rapid. The segmentation of the cells becomes less rapid as the fetus develops, and even yet less rapid in the growth of the puppy after birth and up until maturity, when it is only adequate for replacement of tissue and not at all for growth. However, despite the retarded rate of segmentation, as the organism becomes larger and larger there are so many more cells to proliferate that the rate of total growth gathers momentum.

As the fetus grow, the uterus grows and stretches, stuffed like a two horned sausage.

Externally, while some change in the mammary glands may be noticed earlier, no enlargement of the mother's abdomen is apparent before the fifth week after she is bred, and more frequently it is the sixth week before one can be reasonably certain that she is in whelp, i.e., pregnant. Sometimes there is doubt of her pregnancy up until the very time she whelps her puppies, but it is usually apparent by the sixth or seventh week from the enlargement of her abdomen that she is entertaining guests within. In the doubtful cases, listening on a stethoscope would reveal the heartbeat of living fetus is even when the dam's abdominal enlargement failed to betray their presence.

Hence, little can be guessed from the external appearance of the mother about the number of puppies she is about to litter.

On the other hand, sometimes, but rarely, a bitch may give every external indication of being pregnant, with enlarged abdomen and developed breasts, even with a flow of milk, and yet may prove not to be in whelp. She may even make a bed for her litter. At the end of nine weeks from her menstrual season, the enlargement of belly of such a one recedes. She may accept and suckle puppies from another bitch, but in her own case it is a matter of hope deferred.

All during the pregnancy, and even before, the corpus luteum, the follicle in which the ovum had grown and ripened, a benevolent little busy-body and master of ceremonies, has been sticking its figurative nose into the internal economy of the mother. Once assumed to be merely an envelope to enclose the ovum, it is now known to function as a gland of internal secretion, i.e., an endocrine gland, sending its hormones through the blood stream on all kinds of imperious errands.

The hormones from the corpus luteum stimulate the development of the mammary glands, the secretion of milk in them, and are believed to affect markedly the general metabolism of the pregnant bitch.

The active life of any corpus luteum is limited and by the end of nine weeks the hormones from it have lost their authority— their work has been accomplished. No longer do they inhibit the whisperings to the uterus of the hormones from the pituitary gland that the star boarders will never pay their bills and had best be thrown out on their heads. Corpus luteum had constantly counseled the uterus to be patient, to give them time.

Aware that its counsel of patience to the uterus will not be heeded for long, the corpus luteum takes steps to soften the junction of the two halves of the pelvis to make easier the exit of the fetus, when the uterus shall finally give them notice to go. And some secretion from the ovaries, either one from the corpus luteum or from the female interstitial gland, activates the mother to prepare a bed for the impending birth. At the end of nine weeks, the corpus luteum ceases to function, the uterus heeds the advice of the pituitary gland, and both literally and figuratively clamps down upon her no longer welcome guests.

If the hormone from the pituitary is not strong enough to force the uterus to expel the matured fetus, it is often necessary for the veterinary obstetrician to strengthen the action by injection into the blood stream of the mother of a pituitary extract to produce greater uterine contractions.

The bitch, left to herself, has prepared a bed by digging a hole in some sheltered ground. Most dog breeders aid their bitches by furnishing them with a suitable whelping place, which should be warm and dry, secluded from possible disturbance by dogs or people. When the bitch is about to whelp she may be nervous and restless for a day or two with premonitions of her ordeal.

After the bitch has whelped her litter, her uterus, which had grown and stretched to accommodate them, gradually shrinks until it is again of the size it was before the pregnancy.

The period of gestation, the duration of normal pregnancy, in the dog is generally reckoned at sixty-three days. While that is by no means the maximum, it is in actual fact somewhat longer than the average pregnancy. Puppies whelped at any time after the fifty-seventh day cannot be considered as seriously premature. It is without any intention to discredit tales of thriving puppies born on the fifty-third day that we offer the caution that misalliances are not unheard-of in dog breeding and keepers are not always as careful of their records as might be wished. It is that, also, which makes hazardous the acceptance of statistics about the matter and the categorical statement of any normal gestation period.

Late births, sometimes as late as the seventy-fourth day, may be due to the ripening of the ova several days after copulation, although the possibility of an unrecognized and unrecorded breeding is not to be overlooked in such cases.

The presence of milk in the breasts is not a sure sign of approaching parturition, nor is its absence indicative that the bitch's time is not yet, to use a Biblical phrase. Milk is to be found in the breasts of some bitches several days before they whelp, and in some it does not appear until hours after all the puppies are born. Indeed, milk sometimes appears in the breasts of bitches some nine weeks after their menstrual period even if they have not been pregnant at all.

The bitch usually gives birth to her young without great difficulty and without manifestation of excessive pain. When labor is normal, the less human obstetrical assistance offered her, except praise, sympathy, and encouragement from a beloved master, the better off she and her puppies will be. She will usually refuse food for several hours before the onset of labor, which may last from three to twelve hours, or even longer, before the appearance of the first puppy. The pains of labor often make a bitch restless. She goes off into a dark, secluded place, or scratches at her bed, rearranging it. She may whimper or moan in a plea for sympathy. She is likely to squat in a urinating position.

Most puppies are littered between midnight and morning, although some bitches are much more leisurely in their whelping and twenty-four hours between the delivery of the first and last pup is by no means unheard-of.

In the passage of the fetus through the os uteri, the foetal membrane is burst and the amniotic fluid is released to flood the vaginal passage, lubricating it and sterilizing its mucosa. The bitch makes a muscular contraction and the puppy is born. He is wrapped in foetal membranes which the bitch normally removes from him with teeth and tongue. Following the puppy and attached to him by means of the umbilical cord is the placenta which the bitch will eat, severing the cord with her teeth.

Many breeders choose to sever the cord themselves, lest the bitch bite it too short, and for bitches with badly undershot or uneven mouths, this assistance may be quite essential to the life of the puppy. If this is done, the cord should be tightly bound with a sterile thread some three or four inches from the puppy's belly and severed with sterile scissors. The remaining portion will dry and stuff off in the course of a few days. Hemorrhage may result from cutting it too short or from the bitch's biting it too short.

Whether or not the bitch be permitted to sever the cord, she should in any event be allowed to eat the afterbirth. Some persons are nauseated at this normal habit of the bitch but the eating of the placenta is known to stimulate the secretion of milk, and it should not be interfered with. (The human female is not at all loath to take and is, indeed, given placental extract, in an unrecognizable form, of course.)

The bitch licks the puppy dry and her massage of it compresses the small ribs and the puppy breathes and grunts. If the membrane is not quickly removed from its head after its advent into the air, it smothers and dies.

Thrust headlong into a big world, it is forced to breathe for itself and to forage for its food. Instinctively, it makes toward the teats of its mother's breasts and, its quarters braced against the floor of the nest, treading, straining, sucking, it obtains the exercise as well as the nourishment which enables it to grow. The breeding process is finished: the miracle of reproduction has been wrought. Two gametes have fused to form a zygote which proliferated into an embryo, later to be known as a fetus . Forced from the mother's uterus into this breathing world, that fetus is now become a dog.

In the zygote was all that this organism could ever be. In the puppy is all that the dog may become. Only the optimum of environment will permit this newborn dog to realize all the possibilities of maturity inherent in him. However good a puppy it may be, subject it to an unfavorable environment and it will fail to be the mature dog for which we hope.

Food, housing, exercise, grooming, and training—all those are the problem of the keeper, not of the breeder, although keeper and breeder are frequently, even usually, one and the same person. The litter safely launched in the world, the breeder's task is done, be it well or be it ill, until the puppies are mature and another generation must find its mates. Again the keeper must retire and the breeder once more assumes command.

The pregnancy just described may be taken as the normal one. Any one or several of many abnormalities may occur to cause the breeder much concern and possibly to nullify all his efforts. Well kept dogs are, as a lot, normal in their reproductive processes but they vary somewhat, one from another, and accidents do occur.

We have seen that tubal pregnancy sometimes occurs and requires surgery to prevent the death of the bitch. Another hazard is the death of the embryo at any of its stages, due to any one of many causes including malnutrition, poisoning, or a blow to the bitch. Abortion may, of course, occur at any stage of the pregnancy and is usually the result of excessive and unusual activity or excitement of the bitch or to some accident to her.

Most bitches deliver their puppies without excessive difficulty for themselves or for their keepers, but there are obstetrical circumstances which must be watched for. Labor pains and uterine contractions may be too weak to dislodge the fetus. The pelvis may be too contracted and narrow to permit of the passage of the fetus . Scar tissues or tumors may obstruct the vaginal passage. One or more of the fetus may be abnormally big, a monstrosity. One or more fetus may enter the vagina breech first or in some other abnormal presentation. Or even, though rarely, there may be a torsion of one of the horns of the uterus.

Any of these abnormalities demands the services of an expert obstetrical veterinarian, and it is a wise dog breeder who, in advance of his emergency, decides what man he is to call. It is desirable to choose a veterinarian in whom one can have utter confidence and to accept his advice and decisions unconditionally.

Sometimes Caesarian section is indicated, and in the hands of a clever and experienced veterinary surgeon it is not a difficult or very hazardous operation. It is certainly an interesting one to watch. If it is in all ways successful, the bitch may be in her bed suckling her puppies in less than an hour from the time she goes on the table. The operation does not necessarily interfere with subsequent use of the bitch for breeding. It is resorted to most frequently in small breeds with large heads, such as Bulldogs, French Bulldogs, and Boston Terriers.

Amateur obstetrics in complicated cases often results in much trouble, the loss of the litter, infection of the bitch and her possible death. Bitches do not in most cases require professional assistance in parturition but amateur bungling cannot take its place when it is needed.

Puppies are blind at birth, at least their eyes are not to open for some eight to twelve days. It is a wise and experienced breeder, indeed, who can sort a litter of puppies for their comparative excellence at the time of their birth, and even a wiser breeder who reaches the conclusion that such evaluation so early is almost, if not entirely, impossible.

It is true that some serious deformities and malformations can be detected and the defective puppy can be destroyed as not worth the rearing. Among these undesirable attributes which should be eliminated are hare-lips, cleft palates, the absence of an essential member such as a leg or foot, short tails on long tailed breeds, or long tails on naturally short tailed breeds. It is better to get rid of such defectives, which are few among judiciously bred dogs, and to devote all of one's energy to the rearing of the sound and promising rather than dissipate care upon the unfit.

However, it may be well to give warning that the comparative sizes at birth of the members of a litter provide no final criterion of their comparative sizes at maturity. The smallest puppy in the litter may develop into the largest dog. Hence it is unwise to base eliminations upon size alone.

Color and markings at birth are subject to some change with growth. Many a litter of Dalmatians has been destroyed at birth by ignorant breeders because the puppies were completely white, as they always are in that breed, the black spots appearing later. Colored patterns are likely to enlarge, white to decrease. Nose bands, face blazes, white collars, will grow narrower in proportion to the colored pattern as the puppy matures. Small spots of white on toes or chest may entirely close up and disappear. Breeds of a black and tan pattern, such as Airedale Terriers, Manchester Terriers, and Doberman Pinschers, are born with a much larger proportion of black and much smaller proportion of tan than they are to possess later on. Yorkshire Terriers are almost black and tan at birth, their true color developing later. And so, caution must be used not to bucket a newborn puppy which is only apparently, and not really unrepresentative of the breed of its parents.

Happily, there is no law to restrain the destruction of the newborn, unfit dog.

These considerations belong not strictly to a discussion of pre-natal life. But the new-whelped litter is the end and reason for pregnancy. Only he who has squatted by a stream rocking a gold pan and found among the black sands in its bottom tiny nuggets presaging checks from the mint, knows a kindred thrill to that of the dog breeder who handles and examines a newborn litter from his favorite bitch. What visions of triumphs in the show ring, ribbons, and silver cups, and championships these grunting whelps evoke! The sire expertly chosen to complement the dam in pedigree and type, the bitch conditioned and nourished and coddled to give these potential paragons the optimum of environment those nine, warm weeks within her womb; here in their nest, squirming and nuzzling, are the dog breeder's achievement. So far as pertains to this particular litter, his work as a breeder is at an end. What he will do with these newborn puppies as keeper, rearer, and exhibitor is outside our province and beyond the scope of this book.

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