Smallwood and Rogers, Molluscan Nerve Cells. 6i 



of Montgomery, the vacuolar spaces of Hamaker, the granules 

 within clear spaces of Rand, the numerous vacuoles described 

 in Arion by Legendre, all, we believe, are to be classified as 

 nerve cell vacuoles. The significance of these vacuoles is dis- 

 cussed further on. 



v. the nissl bodies. 



Rhode ('04a) has called attention to certain similarities of struc- 

 ture in the ganglion cells of vertebrates and invertebrates. Both 

 have the following facts in common: (i) a homogeneous hyalo- 

 plasm, (2) a spongioplasmic groundwork which consists of coarse 

 and fine fibrils, (3) a stainable substance which in the case of the 

 invertebrates and a part of the vertebrates is lodged in the coarse 

 fibrillar spongioplasm. In the remainder of the vertebrates it 

 clumps and forms the Nissl bodies, which are, indeed, independ- 

 ent of the spongioplasm, which appears between them in almost 

 colorless fibrils. 



The structures known as Nissl bodies or granules furnish a 

 most interesting field of research. The great degree of variability 

 in the appearance of nerve cells from different animals has led to 

 the belief that structures existing in one nerve cell may have no 

 counterpart in another. Among the invertebrates the failure of 

 some authors to identify structures closely similar to those found 

 in vertebrates has led to the supposition that such structures were 

 lacking. It seems evident that such bodies as Nissl granules 

 must be present in the cell for some specific purpose. The nerve 

 cells of invertebrates have fundamentally similar functions to per- 

 form as the cells of vertebrates. If this be true, may we not expect 

 to find some structure, perhaps even morphologically and chem- 

 ically different, which takes the place of that structure known as 

 the Nissl granule .? We are of the opinion that such bodies do 

 exist. 



The stainable structures of the cell, referred to above, have 

 received various names, as they have been observed and described 

 by different authors under dissimilar conditions. The terms 

 chromatic substance, chromophile substance, tigroid substance, 

 sigroid substance, basophile constituent, etc., have all been em- 

 ployed to designate the structures recognized by us as Nissl bodies 

 or Nissl granules. Various authors have recognized the fact that 



