Striking changes occurred in the skull; for example, there was a shortening of the snout and jaws and at the same time a reduction of the number of teeth (dog, cat, cattle, pig). The shortened snout and accentuated rounded eyes induced the juvenile appearance of the "eternal cub." It also resulted in lower brainpower and smaller brain volume. The skeleton became less resistant than that of wild animals as a consequence of the "comfortable life" with its lack of movement. For the same reasons, the size of some of the physical organs decreased, for example, the heart (35% lower by weight in the domestic rabbit when compared to its wild ancestor). Of course there are exceptions. The English thoroughbred, trained for several centuries for racing, has a heart about one fifth heavier than that of other horses of the same size. The fat storage mechanism has also been modified by domestication. In wild animals, fat is stored in the surroundings of the
if they come in contact with them at all. They are denied the learning that parents teach their offspring in the wild.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.