CHAPTER X 

 THE SUMMARY OF PART II 



1 



The essential component of the protoplasm is a protein of globulin 

 nature, molecules of which exist in parallel alignment in a stretched 

 thread-like form, associating with one another in a regular array by 

 a physicochemical force. Lipids are other important components, which 

 are inserted among the protein molecules. Owing to the lipids, pro- 

 toplasm can exhibit px'operties of a liquid, and protein molecules 

 existing in it can change freely their structure ; at the same time 

 protoplasm itself can possess the specific configuration. 



If the protoplasm is such a system consisting of molecules of 

 protein and lipid, each of which associating regularly with one an- 

 other to form a certain structure, it will be expected that a change 

 arising at a site of the protoplasm will spread to other parts. Actually 

 this appears to be the case ; for example, it is known that, when an 

 adequate stimulus is applied to the protoplasm, there occurs at the 

 site of stimulation a coagulation of protoplasm into minute particles, 

 which spreads succesively through the whole protoplasm. 



The protoplasm coagulation into such minute particles can be 

 explained on the assumption that the thread-like protein molecules 

 exist in forming bundles in parallel alignment, each bundle being 

 formed by several hundreds of threads. This bundle is assumed tO' 

 be the unit of protoplasm, and termed "elementary body of protoplasm." 

 Lipids are inserted among protein molecules in this unit body, and the 

 protoplasm is composed of these bodies which are arranged in parallel 

 array, combining loosely with one another by a physicochemical 

 force. 



The thread-like protein molecules forming the body will contract 

 or fold when a stimulus is given, so that the protoplasm as a whcle y^a»,kt 

 coagulated into the unit particles by the stimulus. Since this coa- ^ 

 gulation of protoplasm, that is, the folding or contraction of the pro- 

 tein molecules, is reversible, the folded or contracted molecules vrill 

 restore the stretched form when the stimulus is removed, whereby the 

 protoplasm recovers its original state. 



On the other hand, as regards its function the protoplasm is a. 



