AN INTRODUCTION 

 TO SEXUAL PHYSIOLOGY 



CHAPTER I 



INTRODUCTORY 



As is well known to every student of biology, all living organisms, 

 both vegetable and animal, consist of one or more cells. Each 

 cell is composed of protoplasm which is the physical basis of all 

 life, and the vital substance forming the most highly developed 

 animals differs in degree rather than in kind from the undiffer- 

 entiated protoplasmic mass comprising the most simple form 

 of life known. Protoplasm itself is a semi-fluid, transparent, 

 viscous substance made up chiefly of nitrogenous compounds 

 or proteins, but containing also small quantities of fats and 

 carbohydrates together with sulphur and phosphorus in a com- 

 bined form, as well as certain metals. It is generally enclosed 

 by a membrane which consists of the outer layer of the cell, and 

 within it is a small, round specialised body known as the nucleus, 

 which can usually be easily identified under the microscope by 

 its more intense staining capacity. The nucleus is essential to 

 the life of the cell. 



The simplest forms of animals .and plants are unicellular, 

 and of these the amoeba, a microscopic organism found in pond 

 water, is a well-known example. In this animal all the vital 

 functions of the body are discharged by one cell which may be 

 seen to move spontaneously by protruding a part of its substance, 

 to eat up small particles of food by permitting a portion of its 

 protoplasmic contents simply to flow round them, to excrete waste 

 products, to increase in size, and, finally, at a certain stage of its 

 life history, to reproduce by a process of dividing into two. This 

 is the simplest mode of generation found in any organism and 



