PART I 



SECTION I 



PROTOPLASM 



THE first step in the study of physiology must be to acquire 

 as clear and definite a conception as possible of the nature 

 of protoplasmic activity in its most simple and uncomplicated 

 form, for in this way an idea of the essential and non-essen- 

 tial characteristics of life may best be gained. 



I. Structure. Protoplasm is a semi-fluid transparent 

 viscous substance. It usually occurs in small individual 

 particles CELLS more or less associated, but it may occur 

 as larger confluent masses PLASMODIA. 



Sometimes protoplasm seems perfectly homogeneous, but 

 generally a reticulated appearance can be made out even in 

 the living condition (Fig. 1), and from this it has been con- 

 cluded that there is a more solid part arranged like the 

 fibres of a sponge, or like the films of a mass of soap- 

 bubbles, with a more fluid interstitial part. In all proto- 

 plasm, therefore, there seems to be a certain amount of 

 organisation, and in certain cells this organisation becomes 

 very marked indeed. 



II. Physiology. A knowledge of the essentials of the 

 physiology of protoplasm may be gained by studying the 

 vital manifestations of one of the simplest of living things, 

 the yeast plant (Saccharomyces Cerevisae). 



This plant consists of very minute oval or spherical bodies 

 frequently connected to form chains, each composed of a 

 harder outer covering or capsule and of a softer inner sub- 

 stance which has all the characters of protoplasm. 



