8o NERVOUS SYSTEM OF VERTEBRATES. 



nessed. It was further observed, however, that after a few days 

 the functional responses ceased, presumably because of the death 

 of the nerve fibers whose cell-bodies had been cut away. 



It was supposed by tlie older anatomists and physiologists 

 that the dendrites of a nerve cell were merely protoplasmic expan- 

 sions which served to absorb the nutrient materials necessary for 

 the cell, and they were called " nutritive processes. " It was thought 

 that the cell-body and neurite carried on all the specific nervous 

 functions. Since it has been shown that the dendrites play apart 



Fig. 40. — A cell from one of Bethe's figures to illustrate the experiment described 

 in the text. The arrow shows where the single process was cut. 



in the nerve activities not less important than that of the cell- 

 body and neurite, they have not on that account lost their impor- 

 tance for nutrition. Since they offer by far the greatest surface 

 for absorption of nutriment, together with a sufficient bulk of 

 protoplasm for the purpose, it is probable that absorption does 

 take place chiefly through the dendrites. But the final result 

 of Bethe's experiment shows that the cell-body, or more especially 

 the nucleus which it contains, is necessary for the nutritive activi- 

 ties. In nerve cells as in other cells the nucleus plays an essential 

 part in the metabolic processes. Deprived of its nucleus the nerve 

 cell soon dies, although it may carry on its normal functions so 

 long as the nutrient materials contained in the protoplasm suffice 

 for the necessary metaboHc activities. 



