Page:A Text-book of Animal Physiology.djvu/61

Rh ear, nose, tongue, and the entire surface of the body—are faithful reporters of facts. They put the inner and outer worlds in communication, and without them all higher life at least must cease, for the organism, like a train directed by a conductor that disregards the danger-signals, must work its own destruction. Without going into further details, suffice it to say that the processes of the various cells are subordinated to the general good through the nervous system, and that susceptibility of protoplasm to stimuli of a delicate kind which enables each cell to adapt to its surroundings, including the influence of remote as well as neighboring cells. Without this there could be no marked advance in organisms, no differentiation of a pronounced character, and so none of that physiological division of labor which will be inferred from our brief description of the functions of a mammal. The whole of physiology but illustrates this division of labor.

It is hoped that the above account of the working of the animal body, brief as it is, may serve to show the connection of one part functionally with another, for it is much more important that this should be kept in mind throughout, than that all the details of any one function should be known.

In order to enable the student the better to realize the nature of living matter or protoplasm, and to render clearer the distinction between the forms that belong to the organic and inorganic worlds respectively, we shall make some comparisons in detail which it is hoped may accomplish this object.

A modern watch that keeps correct time must be regarded as a wonderful object, a marvelous triumph of human skill. That it has aroused the awe of savages, and been mistaken for a living being, is not surprising. But, admirable as is the result attained by the mechanism of a watch, it is, after all, composed of but a few metals, etc., chiefly in fact of two, brass and steel; these are, however, made up into a great number of different parts, so adapted to one another as to work in unison and accomplish the desired object of indicating the time of day.

Now, however well constructed the watch may be, there are waste, wear and tear, which will manifest themselves more and