The subject of physiology treats of the study of the phenomena occurring in all living things but for the present purposes it is limited to the study of the activities of theanimal body especially that of man It is part of the greater subject of biology or the study of living things.
In making such a study we can approach the subject in a number of ways.
Fromanatomy we learn the gross structure of the body, and from histology, which is the study of its microscopic structure; we get a firmer basis from which to infer a possible function. We learn, for example,that the bodies of animals are composed of cells of great variety and that each organ has its own specialized cells arranged in a definite pattern. The appearance of the cells is often distinctive andmay tell as whether they are protective, secretory, and nervous or connective.
By a chemical study of the tissues and of the various substances found in living things and of those taken intothem, we can relate to each other the various chemical processes which take place as if they were carried out in a chemical laboratory. This constitutes biochemistry. From it we learn how the body breaksdown the various substances found in nature, makes use of them, and returns to its environment those it does not need or has used.
By a study of the movements and other physical processeswhich take place in the body (biophysics) we understand the mechanics and dynamics of the body. From this we understand, for example, how the blood circulates and how air is sucked into the lungs.Physical chemistry, too, adds its quota and indicates such things as the principles by which substances may pass through the various membranes of the body especially those of the cells themselves.In biology we trace the structural functions of organs of lower animals and how they have been evolved, and we see how, as we go down the animal scale, the processes become simpler and simpler...