48 'Journal of Comparative Neurology and Psychology. 



be traced directly into the surrounding neuroglia tissue and appear 

 to be of a more permanent character than the vacuoles. We are 

 inclined to believe that these lymph canals are supplied v^ith defi- 

 nite walls. 



A sufficient number of cases has been described to show that 

 occasionally nerve cells are actually penetrated by capillaries. 

 We have observed one instance in Helix. "These capillaries ter- 

 minate in finger-like branches or pass through the cell or even 

 through two or three adjacent cells. They have a definite wall and 

 contain blood corpuscles. 



The question as to how the nerve cell is nourished, and how 

 it maintains itself during long periods of excitation, long fasts or 

 hibernation is one which has attracted the attention of scientists 

 and will continue to do so. The appearance and disappearance 

 of the granular particles in the cells at once gives evidence that 

 they are temporary structures. It is natural to think of nerve 

 cells as performmg one function, and we frequently lose sight of 

 the fact that the cell has a protoplasmic structure which must be 

 nourished just as truly as that of any other cell. The activities 

 of a nerve cell are not all of a nervous character; metabolic 

 processes must go on here just as truly as in the muscle cell or the 

 gland cell. But these processes may be overshadowed or concealed 

 by the more specialized activities of the cell. 



We shall attempt to show that these metabolic processes actually 

 take place within the nerve cell, that certain food substances are 

 stored up within the nerve cell, that these substances may remain 

 in the cells for long periods, and that they may be called upon at 

 any time of want or stress to supply material out of which new 

 protoplasm may be built or to act as a source of energy. 



Twenty years after the admirable work of Nansen, we can do 

 no better than to quote from him the following sentence. "If 

 we look through the modern literature having special reference to 

 the invertebrate nervous system, and compare the many difi^erent 

 views of the structure of the ganglion cells, we meet with a con- 

 fusion on the subject which is far from encouraging. " 



II. MORPHOLOGY OF THE GASTEROPOD NERVOUS SYSTEM. 



Much of the work on nerve cells where a direct stimulation has 

 been employed has been on a certain ganglion through a specific 



