Law of Proenviron]ment 235 



be least permanent and abundant in simpler metazoan nerve 

 cells, but should increase in aspect and quantity along the 

 metazoan scale ; should be most regular and fully formed during 

 a rest period; should be reduced in number, in size, in regu- 

 larity, or in density during fatigue; and should show certain 

 micro-chemical characteristics. The small bodies that have 

 been called Nissl's granules, and whose substance we propose 

 to term neuratin^ answer to all of the above requirements. 



During the past ten years an increasing literature on these 

 has appeared, and study of this literature may now be sum- 

 marized. The investigations of Nansen, Pflucke, McClure, 

 Rhode, Legendre, and Smallwood amongst others on inverte- 

 brate nerve cells, and those of Fleming, Cajal, Held, Marinesco, 

 Gehuchten, Ewing, Carrier, Lugaro, and Ranson on the nerve 

 cells of vertebrates, show that definitely arranged and stain- 

 able bodies occur in the protoplasm of the nerve cell around 

 the cell-nucleus. These have variously been called tigroid, 

 sigroid, basophile, chromophile, and Nissl granules or sub- 

 stance. Amongst invertebrates various worms, nemerteans, 

 molluscs, crustaceans, and insects have mainly been studied. 

 In such worms as the Nereidce the granules are usually aggre- 

 gated in the protoplasmic spongework, and in somewhat irreg- 

 ular manner; a similar disposition seems to occur in the nemer- 

 teans studied by Montgomery; in the crayfish and other crus- 

 taceans they are often very abundant, oval in shape, and 

 definitely arranged in concentric rows round the nucleus of 

 each nerve-cell, though at times they are prolonged into the 

 uniting ends of the nerve-fibers. In Mollusca, specially as 

 studied by Smallwood and Rogers alike histologically and 

 experimentally, the granules appear as diffuse or aggregate 

 masses around the nucleus of the ganglionic cells. The above 

 observers conclude (8J^: 63) "that these structures will be 

 found to fill the same place in the economy of the invertebrate 

 nerve-cell as does the Nissl body of the vertebrate nerve-cell." 

 Experimentally also it was found that, alike during progressive 

 starvation and exhaustion by fatigue, the granules are grad- 

 ually reduced in number, or size, and at length disappear. 



