244 



cell itself takes the blue stain relatively deeply, presenting nearly as 

 deep a coloration as the nerve cells. Its irregular fusiform shape 

 makes it at first sight to be taken for a ganglion cell. Under the 

 low power these cells are seen to be disposed in a general way pa- 

 rallel to each other, encircling the heart proper somewhat spirally. 

 (See Fig. 1.) Under the higher powers these cells appear to be irre- 

 gularly fusiform, with protoplasmic branchings extending from the poles 

 of the cell. The central part of the cell body is occupied by a rela- 

 tively large nucleus which measures about 6 f.i hy 4 (.i^ while the cell 

 body measures from 30 {.i to 50 f.i in its longest diameter, exclusive 

 of its protoplasmic branchings. The protoplasm, as seen stained with 

 methylen blue, is coursely granular ; the blue granules floating in the 

 fluid non-staining portion of the cell. Sometimes the granules may be 

 aggregated in one part of the cell, the central part of the cell being 

 more deeply stained for that reason. 



A comparison of these results with those of other investigators 

 shows many conflicting statements. The embryological researches of 

 Van Beneden and Julin, advocated by Delage, Herouard, Herdman 

 and WiLLEY, point to the existance of no endothelial layer; but a simple 

 layer of epithelio-muscular tissue. Lankester, Hermann, Seeliger, and 

 others make the same statement on anatomical evidence only. Lacaze- 

 DuTHiERS, RouLE, VoGT, ScHULTZE and othcrs point out thi'ee layers 

 in the heart proper, an endothelial layer, muscular and connective 

 tissue layer ; some of the above calling the two latter elements a single 

 layer. Later embryological evidence seems to favor the latter view. 

 None of the above mentioned writers have found nervous elements on 

 or near the heart. 



I find nerve cells in two small ganglia at opposite ends of the 

 heart, at about the point where the waves of contraction originate. 

 The cells are few in number; the most found in one ganglion twelve. 

 A few cells are found scattered along the course of the nerve fibers. 

 The nerve cells are nearly all bipolar in Molgula; a few tri- and 

 multipolar cells have been noticed in Yarsis cordiformis zo- 

 naria. In Molgula the nerve fibers appear to almost encircle the 

 heart tube in a somewhat spiral manner. The ultimate ends of the 

 nerve fibrils were not traced. In general the greatest number of nerve 

 cells are grouped at one side of the heart, the fibrils taking a spiral 

 course so as to nearly encircle the heart at that point. In some cases 

 the long axes of the nerve cells take approximately the long axis of 

 the heart and fibrils have been followed for some little distance in a 

 longitudinal direction along the dorsal edge of the heart. (See Fig. 3.) 



