CHAPTER IV. 



THE VITAL CHARACTERS OF ORGANISMS. 



THE manifestation of so-called vital phenomena in man forms 

 the subject-matter of the following chapters, and some kind of 

 explanatory definition of the vital characters of the simpler organ- 

 isms will be useful in preparing the beginner's mind for the more 

 intricate questions in human physiology. This, with the foregoing 

 short account of the chemical and structural peculiarities of ani- 

 mals, will complete a rough outline of the general character of 

 organisms. 



Protoplasm has already been referred to as the material capable 

 of showing "vital phenomena," the most obvious and striking of 

 which are its movements. 



Besides the common molecular or Brownian movement of the 

 granules of protoplasm which may be seen in most cases where 

 fine granules are suspended in a less dense medium protoplasm 

 can perform motions of different kinds which must be regarded 

 as distinctly vital in character. This movement may be said to 

 be of three different kinds, according to the results produced, viz.: 

 (1.) The production of internal currents. (2.) Changes in form. 

 (3.) Locomotion. In reality the two latter are dependent on the 

 first. 



The occurence of currents from one part of a portion of proto- 

 plasm to another can be well seen in vegetable cells, when the 

 cell wall restricts the more obvious change in form or place. 

 Thus in the cells forming the hair on the stamens of Tradescantia 

 Virginica the various currents can be seen in the layers of proto- 

 plasm which line the cell wall. 



The granular particles course along in varying but definite 

 directions, passing one another like foot-passengers in a crowded 

 street. The first and most obvious result of this is, that the vari- 

 ous parts of the substance are constantly brought into contact with 



