44 Bulletin of Lahoratoyies of Denison University [Voi. xii 



that of taste buds within the mouth, viz., the perception of 

 diemical stimuli. 



In 1870 the same author (F. E. Schulze, '70) made a 

 further important contribution to the problem of the terminal 

 buds by the demonstration that they differ structurally from all 

 neuromasts, or organs of the lateral line system. The neuro- 

 masts are commonly sunken below the skin in canals, tubes or 

 pits, but in some cases they are strictly superficial and resem- 

 ble in external form the terminal buds very closely, a feature 

 which led Leydig ('5 I, '79, '94) and others to assume that the two 

 classes of organs are mere varieties of a common type. Schulze 

 showed that the neuromasts can in all cases be differentiated 

 from the terminal buds by the fact that their specific sensory 

 cells (pear cells) extend only part way through the sensory epi- 

 thelium and fail to reach the internal limiting membrane, while 

 in the terminal buds both specific sensory cells and supporting 

 cells pass through from external to internal limiting membrane. 



This distinctioTi was confirmed by Merkel ('80) who, with 

 • curious inconsistency, while recognizing the structural dissimi- 

 larity of the two classes of organs, nevertheless, as we shall see 

 below, ascribes to both essentially the same function, touch. 

 This matter was put to the decisive test in my contribution on 

 Aineiunis ('01), a type which possesses both terminal buds and 

 neuromasts in great abundance and diversity of forms. Schulze's 

 contention is supported both by the structure of the organs and 

 by their innervation ; for I have shown that all neuromasts, of 

 whatever form, are innervated by acustico-lateralis nerves from 

 the tuberculum acusticum of the brain, while all terminal buds, 

 whether within the mouth or in the outer skin, are innervated 

 by communis nerves related centrally to a single center within 

 the brain. This center is bi-lobed, the lobus vagi receiving 

 most of the communis fibers from the mouth cavity by way of 

 the vagus and glossopharyngeus and the lobus facialis the com- 

 munis fibers from the terminal buds of the outer skin by way of 

 the facial nerve (cf. Fig. i). 



