SPECIES IDENTITY OF NUCLEUS-PLASMA NORM 491 



excess supply of food, so far as this latter principle is concerned, 

 cannot affect directly the reciprocal relation of plasma to nucleus 

 in the nerve cell. Food is eliminated as a factor on the active 

 side. 



Of course, food may affect the relation in the nerve cell in- 

 directly through its known injurious effects on related systems 

 and organs, which may react as either overf unction or depression. 

 But the nerve cell is par excellence a working cell, specialized 

 for that alone, in no sense a storehouse of food, and so it seems 

 likely that it only takes what food it needs according to its state. 

 I have seen nothing in the resting or functioning cell that indi- 

 cates an excessive piling up of food material, and depression, 

 in which it is such a prominent feature, proves that it could be 

 seen. However, as this must be yet largely theoretical, it must 

 be said to cover the possibilities, that in so far as overnutrition 

 can be a factor, it would lead to depression and eventually to 

 depressant atrophy, as has been proved most conclusively for 

 the Protozoa (Hertwig). So on the passive side overnutrition 

 cannot yet be eliminated as a factor of .depression, affecting as 

 such both resting and functioning cells. 



The deficiency and the absence of food have an established 

 place. Food is a condition of life, and Verworn has pointed out 

 that the absence of any such factor is primarily potent in pro- 

 ducing pure depression. Thus by starvation R. Hertwig and 

 his pupils produced profound depression in the Protozoa and 

 this has been confirmed for the nerve cells of the cat by Mr. T. K. 

 Kruse in this laboratory. However, in harmony with the usual 

 belief that the nervous system is spared at the expense of other 

 organs, the depression produced, even after considerable time, 

 was only moderate in degree. Absence of food, therefore, is 

 only one type of the depression group. 



In conclusion, so far as concerns the resting cell as such, it 

 appears established both on a rational and experimental basis 

 that the sole factors which can alter its constant nucleus-plasma 

 norm are two, functional senility and functional depression. 

 For the resting state, the law of species identity applies outside 

 of the working of these two factors. 



