156 PRINCIPLES OF PHYSIOLOGY 



as the outer tissues are concerned, there is 

 always the internal medium, the lymph. 

 This supplies the living cell with matters 

 prepared, as we have seen, by complicated 

 processes, and now fit for assimilation. The 

 lymph also supplies the living matter with 

 oxygen. How they are actually assimilated 

 we do not know ; we are now in the most hidden 

 region of life. In the cell we find living proto- 

 plasm, and along with it, in many cases, 

 probably in all cases at some period or other 

 of the life of the cell, matters that have been 

 stored up so as to form the elements of 

 secretions, or the substances necessary for the 

 vital activities of the cell. 



As examples, takes the granules in a secret- 

 ing cell which has rested for some time, or the 

 granules in nerve cells, after a period of rest. 

 If we call the protoplasm a and the stored 

 matters b, we do not know whether b has at 

 one time been part of a, or whether a, by some 

 hidden chemistry, has made b outside of its 

 own substance. But there is also inter- 

 cellular matter, which we may call c, and which 

 has been formed by a. Such inter-cellular 



