Smallwood and Rogers, Molluscan Nerve Cells. 67 



Two possibilities for the increase in the number of bodies in the 

 vacuoles present themselves, either the bodies are to be considered 

 as storage products which may be called upon in time of stress to 

 supply energy for the nerve cells or they are to be considered as 

 degeneration products which have accumulated in the cell during 

 the increased activity of the animal in the active season. If they 

 are of the former class, any great increase in the activity of the 

 animals should have the effect of breaking them down and should 

 cause them to disappear. If they are of the second class, pro- 

 longed activity should bring about an increase in their number and 

 size. 



Fatigue. — Hodge and others have noticed that the nerve cells 

 of animals respond to excessive stimulation in definite ways. 

 Hodge found that the cytoplasm of the cells took on a different 

 appearance and that the nucleus became shrunken. Our work 

 upon Limax has failed to confirm these particular observations 

 and has convinced us that we have here conditions which may have 

 escaped notice. 



An active, living, specimen of Limax was taken and by means of 

 an induction current applied to the posterior part of the body forced 

 to crawl until it could no longer draw itself away from the point of 

 stimulation — a period varying somewhat with different specimens, 

 but usually from one-half to three-quarters of an hour. The nerve 

 collar was then dissected out, fixed, sectioned and stained in the 

 usual manner. The nerve cells of an animal treated in this way 

 differ in a very marked degree from those of the normal rested 

 animal. In the periphery of the nerve cells are to be found the 

 vacuoles to which attention has already been called. These 

 vacuoles are usually numerous, but differ from those found in the 

 normal, well fed, rested specimens in that they contain no dark 

 solid bodies. The limits of the vacuoles are sharply marked. 

 The vacuoles appear in various parts of the cytoplasm and may 

 occupy nearly all the space between the nucleus and the cell wall, 

 when at their greatest development. It is evident that these vac- 

 uoles are filled with a hquid substance, for when the cells are placed 

 in a medium of higher concentration than the body liquids an 

 osmotic action takes place which draws out water from the vacuoles 

 and finally ends in their collapse. 



One may say that the disappearance of the dark bodies from the 

 vacuoles is not the result of the fatigue of the animal, but rather 



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