Implications of the Theories of Nerve Action 187 



The Real Importance of Loeb's Conception of the Nervous 



System 



First of all, it is with genuine satisfaction that I recognize 

 the eminent service rendered physiology and general biology 

 by this author's experimental investigations on animal ac- 

 tivities. I have long considered that one of physiology's 

 foremost achievements is the clarification of the conception 

 that nerve phenomena, the most characteristic features of 

 which are response to stimuli and the conduction of the 

 effects of stimulation, are not wholly unique attributes of 

 nerve tissue, but are elaborations of attributes inherent in 

 all protoplasm. Perhaps no single physiologist has con- 

 tributed more to this clarification than has Loeb. Par- 

 ticularly important has been his demonstration that nerve 

 centers in the sense of ganglionic masses which determine 

 reflexes are not fundamental to the coordinated and adapted 

 movements of animals ; that reflexes take place in many 

 animals normally and in many others experimentally, where 

 no such centers exist, as for example in the ascidian after 

 the single ganglionic mass is cut out. 



The pertinacity and technical skill with which Loeb has 

 followed up these ideas are highly commendable. By focus- 

 sing attention on the fact that since plants have no nervous 

 system, they are, in so far as they exhibit movement induced 

 by stimuli, illustrations of the principle of protoplasmic 

 response in actually differentiated organic beings ; and by 

 carrying the same conception over into the animal world and 

 demonstrating that many activities here also are dependent 

 upon direct protoplasmic response and not necessarily on 

 a specially differentiated ganglionic mass, he was led to 

 formulate the tropism theory. This theory, as we shall 

 show presently, has a significance which Loeb himself seems 

 not to have fully comprehended, his general standpoint be- 

 ing unconductive to such comprehension. The theory must, 



