PROTOPLASM 



FIG. 2. Diagram to illustrate the alveolar theory 

 of protoplasm. 



alveolar like a mass of foam (Fig. 2) or reticular like a sponge (Fig. 3). 

 In either case this assumes the presence of at least two substances of 

 different qualities. Among these qualities it can be perceived that one 

 substance is of denser and firmer structure than the other, which is fluid. 

 This denser substance, called 

 spongioplasm, forms the matrix 

 according to the alveolar the- 

 ory, or the reticulum according 

 to the reticular theory. Thus it 

 is a continuous and communi- 

 cating mass in both cases, while 

 the fluid material called the 

 paraplasm is considered to be a 

 continuous and communicating 

 mass in the reticular theory 

 only, and is isolated in bubble- 

 like portions according to the 

 alveolar theory. Granules of 

 a much denser material are found scattered about in the reticulum 

 or matrix. They are called microsomes. The alveolar theory is 

 the more probable, at the same time admitting that in many cases 

 and at certain times a thread formation of more or less extent does 

 exist, its threads lying in the inclosing substance of the alveolar 

 matrix. 



Knowing, then, that protoplasm is differentiated structurally in the 

 cell, we are prepared to hear from the chemists again, who tell us that 



protoplasm is not a definite 

 chemical entity, but a combina- 

 tion of several chemical com- 

 pounds united in a physiological 

 alliance, and interacting on one 

 another in such a manner as to 

 produce the phenomena which 

 we take as evidence of existing 

 life. Passing by some of those 

 substances whose position is 

 doubtful, we can say with prob- 



FlG. 3. Diagram to illustrate the reticular theory ability that those of the COm- 



of protoplasm. pounds known as the proteids 



are the principal figures in this alliance and the seat of real life. Though 

 composed of nearly the same materials, they are of very great variety, 

 due to differences in the method of composition of these materials. 

 Several of them are usually concerned in the structure of any given 



