PLATE 1 



EXPLANATION OF FIGURES 



1 to 3 The cells illustrated in the three figures were all drawn from the same 

 section with the aid of the .camera lucida, and for all cells the magnification is 

 580 diameters. I have attempted to reproduce as nearly as possible the actual 

 appearance of the cells, combining to a certain extent different levels of focus. 

 These three figures clearly show that the cells supplying heart muscle (fig. 1) 

 are histologically intermediate between the cells supplying smooth muscle (fig. 

 2) and those supplying striated muscle (fig. 3). 



1 Cells from nucleus cardiacus nervi vagi of lemur. The smallest cell repre- 

 sents probably a transition type to the cell type of figure 2, and this type occurs 

 more frequently in the caudal portion of the vagus sympathetic nucleus where 

 it is found together with the cells of the type shown in figure 2. 580 diameters. 



2 Cells of vagus sympathetic nucleus of lemur which innervate smooth mus- 

 cle. In the oral portion of the sympathetic vagus nucleus these cells occur alone; 

 more caudally they occur together with the cells of the nucleus cardiacus (fig. 1) 

 in the most oral portion of this nucleus. In the caudal portion of the sympa- 

 thetic nucleus such cells probably reappear and are accompanied by the small 

 cell type shown in figure 1 (smallest cell). 580 diameters. 



3 Cells from hypoglossus nucleus of lemur, innervating striated muscle. 580 

 diameters. 



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