Shfldon, Reactions to Chemical Stimuli. 295 



sliaro in the responses secured bj stimulation of the nostrils and body 

 surface generally. It has been shown above that the reactions secured 

 from the former are due to the nerves of general sensation. No gusta- 

 tory nerves, such as Herrick ('01, '03b, '03c) described for the silu- 

 roids, innervate the trunk of the dogfish and there is no evidence that 

 visceral sensory nerves such as Herrick ('99) found in Menidia reach 

 the skin of the trunk in this form. It can be said, therefore, that in 

 the dogfish the reactions secured from all parts of the body, ex- 

 cepting the mouth and ]n-obably largely from that, are due to stimu- 

 lation of the nerves of general sensation. It is appai-ent, however, 

 that the taste buds and nerves are concerned with the responses 

 to bitter substances. These conclusions are supported by Parker's 

 work on Ameiurus, where he secured reactions to this same series 

 of chemical stimuli after section of the recurrent branch of the 

 facialis. His work shows that in the catfish the free nerve- 

 termini react to chemical stimuli, even of a very weak character. 



Griitzner ('94) found that the nerves of general sensation in 

 man are very sensitive to chemical stimuli, experimenting on him- 

 self and the frog with acid, alkaline, salty solutions, etc. This 

 is the only work dealing with this chemical sense in man. Hay- 

 craft ('OOli) comments on the well-known fact that the sensitive- 

 ness of the nasal mucous membrane of man to ammonia and chlo- 

 rine is due to these same nerves. Camerer ('70) obtained taste 

 reactions from papilla-free regions of the mouth. A little later 

 von Vintschgau ('79b) stated that the nerves of general sensa- 

 tion take part in the sense of taste in man. Shore ('92) followed 

 with the argument that salty and sour tastes are largely due to 

 the general sensory nerves. This is based mainly on the fact that 

 by the use of gymnemic acid he rendered the tongue insensitive to 

 bitter and sweet substances without the loss of acid, salty, or 

 tactile sensation. 



He also found that the perception of acids goes fairly well in 

 hand with tactile sensation. In view of the results following the 

 use of picric acid and saccharine on the dogfish, it is interesting 

 to note that Shore obtained no reactions to these substances in man 

 aftei' the use of gymnema. This shows that in man picric nd 



