126 EDWARD F. MALONE 



because the functional relations of the caudal group are not 

 understood, and because the pigmented cells described by Jacob- 

 sohn in man, have not been identified and studied (of course, 

 in lower animals pigment is wanting, although homologous 

 non-pigmented cells may exist). Further subdivision of the 

 sympathetic nucleus, together with a detailed description of the 

 location and extent of the various cell types, the consider- 

 ation of transition types, and of the relations of the nucleus to 

 the cells of surrounding nuclei, must await a thorough study of 

 numerous series of various animals (including man). 



CONCLUSIONS 



1 . The -histological character of a nerve cell is an indication 

 of its function. Differences in connections with portions of the 

 organism which differ merely in spatial relations do not involve 

 a difference in the character of the nerve cells, but are associated 

 merely with the location of the nerve cell; for instance, arm and 

 leg muscles, flexors and extensors are all innervated by the same 

 type of cell, although such differences in peripheral connections 

 correspond to differences in the position of the corresponding 

 nerve cells. 



2. The three types of muscle are innervated by three distinct 

 types of nerve cell, which, however, are related to one another 

 in such a manner that the cell innervating heart muscle is of a 

 type intermediate between the other two types of cells. Heart 

 muscle, smooth muscle, and striated muscle are innervated by 

 cells such as are illustrated in figures 1, 2 and 3 respectively, the 

 cells of figure 1 constituting a type intermediate between the 

 other two. 



3. The nucleus cardiacus nervi vagi is situated in the middle 

 portion of the sjTnpathetic nucleus of the vagus and is composed 

 of cells shown in figure 1. 



4. The time has passed when experimental workers can afford 

 to neglect to inform themselves of the existence of definite types 

 of cells situated in the region under investigation, and to attempt 

 to bring cell character into relation with cell function. 



