THE BASIS OF LIFE 9 



plasm " should be reserved as a synonym for the substance 

 which is most alive, the substance in which chemical change 

 is most active, the substance which has in the highest degree 

 a potentiality of growth. Anatomical distinctions are better 

 expressed in anatomical terms. We shall treat of such dis- 

 tinctions when considering the organization of the cell. 



In the meantime it may be well to consider the attributes 

 which appear to belong to this most-living substance. Its 

 chemical composition can be inferred only from the com- 

 pounds found on analysis to be present in a mass of organ- 

 ized substance which there is reason for thinking was rich 

 in "protoplasm while it was alive. The compounds found vary 

 within certain limits. The quantity of water associated with 

 these compounds is still more variable. Water is essential 

 to the existence of protoplasm. Its power of combining with 

 water in variable quantities is one of its characteristics. 

 Tissue rich in protoplasm yields on an average about 75 per 

 cent, of water. Part of the protoplasm within a cell holds 

 more water associated with it, part less.. 



Closely associated with its power of holding water is its 

 tendency to assume an architectural form. In large vegetable 

 cells, such as those of the hairs within the flowers of Trades- 

 cantia, the protoplasm may be seen, under the microscope, 

 arranged in threads containing granules which are incessantly 

 streaming up and down them. The spaces between the 

 threads are filled with water. Such mobile protoplasm cannot 

 be said to have a structural form. But in the greater number 

 of cells, and especially in animal cells, the protoplasm is dis- 

 posed in a network, with usually a tendency for the strands 

 of the network to set in lines. In attempting to define these 

 very variable networks, the microscopist is obliged to speak 

 with caution. He finds it very difficult to distinguish 

 between appearances which he is justified in regarding as 

 inherent in the cell-substance, whether alive or dead, and 

 appearances which he may have induced by the action of 

 reagents whilst preparing the tissue for examination. Rarely 

 can he assert that he sees a network in a living cell. When 

 examining a dead cell, he is bound to recognize that the pre- 

 servatives and hardening reagents which he used may have 

 caused the proteins to coagulate in a particular pattern. If 



