INTRODUCTION 5 



the tongue, and the skin, with their related structures, constitute, respec- 

 tively, the visual, auditory, olfactory, gustatory, and tactile apparatus, the 

 function of which, as a whole, is the reception of impressions and the trans- 

 mission of nerve impulses to the brain, where they give rise to visual, audi- 

 tory, olfactory, gustatory, and tactile sensations and volitional impulses. 



The brain, in association with the sense organs, forms an apparatus 

 related to mental processes. The larynx and its accessory organs the 

 lungs, trachea, respiratory muscles, the mouth and resonant cavities of the 

 face form the vocal and articulating apparatus, by means of which voice 

 and articulate speech are produced. The functions exhibited by the ap- 

 paratus just mentioned viz., motion, sensation, language, mental and 

 moral manifestations are classified as functions of relation, as they serve to 

 bring the individual into conscious relationship with the external world. 



The ovaries and the testes are the essential reproductive organs, the 

 former producing the germ-cell, the latter the sperm element. Together 

 with their related structures the fallopian tubes, uterus, and vagina in the 

 female, and the urogenital canal in the male they constitute the repro- 

 ductive apparatus characteristic of the two sexes. Their cooperation results 

 in the union of the germ-cell and sperm element and the consequent develop- 

 ment of a new being. The function of reproduction serves to perpetuate 

 the species to which the individual belongs. 



The animal body is therefore not a homogeneous organism, but one 

 composed of a large number of widely dissimilar but related organs. As 

 all vertebrate animals have the same general plan of organization, there is a 

 marked similarity both in form and structure among corresponding parts 

 of different animals. Hence it is that in the study of human anatomy a 

 knowledge of the form, construction, and arrangement of the organs in 

 different types of animal life is essential to its correct interpretation; it 

 follows also that in the investigation and comprehension of the complex 

 problems of human physiology a knowledge of the functions of the organs 

 as they manifest themselves in the different types of animal life is indispen- 

 sable. As many of the functions of the human body are not only complex, 

 but the organs exhibiting them are practically inaccessible to investigation, 

 we must supplement our knowledge and judge of their functions by analogy, 

 by attributing to them, within certain limits, the functions ^ revealed^ by 

 experimentation upon the corresponding organs of lower animals. This 

 experimental knowledge, corrected by a study of the clinical phenomena of 

 disease and the results of post-mortem investigations, forms the basis of 

 modern human physiology. 



