The first cell, which results from the uniting of a male cell (sperm)and a female cell (ovum) and is thus the beginning of an dog, is complete in every detail. It is a favorite academic paradox to say that a cell multiplies by dividing, and it is, of course, quite true. If one cell divides into two cells, it has divided, but because it is two, it has multiplied. The two become four; the four, eight. As they go on dividing and thus increasing, different cells become specialized at certain stages. Some may become skin, some liver, some heart, some guerillas, some tonsils, and so forth. There are cells that may never renew themselves: brain cells, for example. Then there are other very special-i zed cells, like those in the hair and nails, that are constantly renewed.They all live together in a happy community or colony, doing their work unless hindered by improper nourishment or crowding (footraces), or disease. And that's what our dogs are big colonies of cells.
The Pituitary. Probably most important as a body regulator is the double-lobed pituitary gland located at the base of the brain, to which it is attached by a stalk. It is incredible that such a tiny organ could be capable of performing the feats it does. Yet its direct and indirect chemical influence on other glands and organs directs them to extraordinary accomplishments. Among its capabilities, it can cause an dog to come into heat; make an un maternal dog become maternal;affect the shedding of the coat; cause a pregnant female to commence labor;stimulate growth and cause gigantism, if overactive;cause stunted growth, if uncreative; cause sexual development; help regulate metabolism of carbohydrates;cause governances, if under active; raise blood pressure.
Because it is so potent, the amount of pituitary hormone required for these tasks is very small.
The Adrenal Glands. The adrenal glands, situated near the kidneys,are also known as the suprarenal glands. They produce epinephrine also called adrenaline a potent chemical that regulates blood pressure by its effect on the heart and blood vessels right down to the capillaries.hese glands also determine in some manner the amount of salt in the urine and affect the use of fat and sugar. Their outer layers secrete substance now being used in the treatment of arthritis.
The Thyroid. The thyroid gland lies in the neck on either side of the windpipe. It is attached to the larynx, so that with every swallowing movement the thyroid is also moved. It secretes an important chemical regulator, thyroxin, which is known to contain about 6o percent iodine .Animals whose diets are low in iodine content become sick, and some young dog develop cretinism a peculiar abnormality not often seen among pets they become dwarfed, stupid, slow, dull, and gross in appearance.
Thyroxin regulates the metabolism, or speed of living, in any dog.Slow, sluggish dog, overweight and phlegmatic, respond with quicker actions, more rapid pulse, restlessness, and sleeplessness when given this hormone. When the gland secretes too much of its regulating substance, the dog becomes nervous, develops a ravenous appetite, wastes away, and exhibits protruding eyeballs and usually an in-crease in the size of the gland itself. (Any such increase is called goiter in man or in dog.)
Parathyroid's. Located beside the two parts of the thyroid are two small glands, the parathyroid's, whose function is the regulation of cal-cum metabolism. If they are removed, a condition known as tertian,involving violent trembling, is established and death ensues. It has been thought that they are also concerned with clamps, characterized by trembling and rigidity in nursing mothers. Injections of parathyroid extract increase the percentage of calcium in the blood, even when none is fed, by forcing the body processes to draw it from the bones.
The Ovaries. Located behind the kidneys in bitches are the ovaries,small organs with several functions, the most important of which is the perpetuation of the species.
The ovaries influence body development even before reproductive functions begin. They control even such a thing as mental interest. If the ovaries are removed long before sexual maturity, an dog grows somewhat ungainly and tends to put on fat more than a littermates ovaries have not been removed. This propensity continues through life. The dog also tends to become an inter sex. A female chick grows hackle feathers like a cock; a female puppy loses some of the charm and grace of the whole bitch; a female kitten tends to grow larger and lazier than her whole sisters.
Working in cooperation with the pituitary, the ovaries initiate the sex cycle (though there is some question as to which gland is of greater importance). Once the cycle begins, the behavior of the female in heat is determined by an ovary-secreted hormone in the blood known as the follicular hormone. This hormone produces the swelling of the vulva,the bleeding well known in bitches, and, after several days, the desire for mating.
The Testicles. Besides producing sperm, the testicles secrete the male hormone, testosterone, which functions in connection with the pituitary gland. Some grave errors were made in the use of testosterone in the mistaken notion that it stimulated the testicles to greater activity. It was administered in great quantities until it was learned that the use of testosterone actually lessened testicle activity and caused the deterioration of the testicles. It was found that the pituitary gland's secretions caused testicle activity and production of testosterone, which in turn affected the maleness of the dog. Some good stud dog have been at least temporarily sterilized by the indiscriminate use of testosterone.
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