132 Journal of Comparative Neurology. 



stained preparations, quite large. Other sensory fibers of the 

 sympathetic terminate in free endings. In a number of methyl- 

 en-blue preparations of the frog's bladder in my possession, 

 such an ending is most clearly shown. In some of the most 

 successful preparations, large medullated fibers can be traced in 

 small nerve trunks, from a point at which such nerve trunks 

 reach the base of the bladder, through several sympathetic 

 ganglia, to their ending. From place to place one or the other 

 of the large medullated fibers, or several such fibers, leave the 

 main trunk and, after traversing a longer or shorter distance, 

 break up into two or three short medullated branches, each 

 consisting of two, three or four short internodal segments. 

 From these short medullated branches, varicose, non-medullated 

 side branches are given off at the nodes of Ranvier, which 

 break up into a large number of finer branches, ending in small 

 bulbous enlargements between the cells of the bladder epithe- 

 lium. The medullated branches after losing their myelin ter- 

 minate in the same way. I estimate that a sensory fiber ending 

 in the bladder of the frog supplies an area of about . 2-. 3 sq. 

 mm. In Fig. 1 1 is reproduced the ending of a sensory fiber in 

 this organ. 



Smirnow (93) has described sensory endings in the heart 

 of amphibia and mammalia ; in the latter both in the endocar- 

 dium and the exo-cardium. The endings are found in the con- 

 nective tissue of the heart and are the terminal branches of 

 large medullated nerves, which, after giving off side branches, 

 lose their myelin and terminate in an end-brush with terminal 

 bulbar enlargements. 



Smirnow has endeavored to ascertain, by degeneration, 

 whether the sensory endings belong to the depressor nerve of 

 the heart. The two experiments, one on the cat and one on 

 the rabbit, in which such degeneration was attempted, gave re- 

 sults which were interpreted as showing that the sensory end- 

 ings in the heart belonged to this nerve. 



I may at this point draw attention to the fact that in our 

 text-books of anatomy it is customary to speak of a sympa- 

 thetic ganglion as having three roots, a motor, a sensory and a 



