174 PEABODY. [VOL. I. 



deeply stained with the blue, the line of separation between 

 the two appearing quite distinct. 



To recapitulate the facts of innervation as given by the 

 methylene blue : Five to seven medullated fibers coming from 

 the (seventh pair of) cranial nerves enter each ampulla from 

 below and pass up the centrum. Just beneath the centrum 

 cap the sheath disappears. The axis cylinders, continuing on 

 their course, send out lateral branches, which after division 

 and ramification beneath the centrum cap run out along the 

 partitions to the outer walls of the compartments. Here 

 minute fibrils play over the bases of the deeper layer of cells, 

 ending in slight enlargements on their surfaces. This much 

 of the innervation of an ampulla has been given sharply and 

 clearly by the use of the methylene blue. Since nothing fur- 

 ther in the way of nerve structure has been suggested by the 

 method, it seems to me the theories of the function of the 

 ampullary organs must conform to these facts. 



Physiology. - - Of the theories thus far suggested to explain 

 the function of the ampullae of Lorenzini, but two are sup- 

 ported by anatomical facts: either they are sense organs, or 

 they are glands for the secretion of mucus. 



The wealth of nerve supply for these organs almost compels 

 one to believe that they must be sensory in character. This 

 theory was first advanced by Jacobson (1813), and in most of 

 the important papers on these organs since that time, including 

 those of Muller (-51), Leydig ('68), Boll ('68), Merkel ('80), 

 Ewart ('92), the writers have maintained the view that the 

 ampullae were sense organs. 



The histological structure of the epithelium lining the 

 pockets does not, however, show the elements ordinarily asso- 

 ciated with sensory epithelium. There is no differentiation 

 into sensory and supporting cells, sensory hairs are absent, and 

 indeed specialized sensory cells seem to be altogether lacking. 

 The nerve fibrils end freely on the lower surface of the cells of 

 the deeper layer. The centrum has been regarded as the most 

 important part of the ampulla, in which the nerves were sup- 

 posed to end. As we have seen, this is not the case. The 

 single layer of cubical cells covering the centrum cap seems to 



