29^^ Jojtriial of Comparative Neurology and Psychology. 



than is the mouth to salts and alkalis. The outer skin and the 

 mouth are equally sensitive to acids, while the mouth is more sensi- 

 tive to bitter substances. 



4. The most sensitive portions of the body ai-e the mouth, nos- 

 trils, anus and iins, while the head is the least sensitive to chem- 

 ical stimuli. 



5. When the spinal cord is destroyed, no reactions are obtained 

 from the caudal part of the body, showing that the lateral line 

 nerves have nothing to do with chemical sensation. 



G. When the -cord is severed from the brain, the caudal ])art 

 of the animal is more sensitive to chemical stimuli than before. 

 There is no spinal shock. 



Y. Section of the olfactory crura and different rami of the tri- 

 geminus nerve show that the extreme sensitiveness of the nostrils 

 to the stimuli used is due to the ramus maxillaris trigemini, a 

 nerve of general sensation, rather than to the olfactory nerve. 



8. Parts of the body fatigued for tactile response always react to 

 chemical stimuli, but when any given region is fatigued for a 

 given chemical it rarely responds to tactile stimuli, although it 

 usually reacts to other kinds of chemical stimuli. 



9. When cocaine is applied to the skin, tactile response disap- 

 pears before chemical. Among the different chemical sense quali- 

 ties, the sensitiveness to bitter disappears first. 



10. This sensitiveness to chemical stimuli is due almost ex- 

 clusively to the nerves of general sensation, not at all to the ol- 

 factory and very little to the gustatory nerves. 



11. Evidence presented suggests that this sense is a true sense 

 quality, with a nervous mechanism distinct from that serving gen- 

 eral tactile sensation. 



12. A true chemical sense is found not only in the invertebrates, 

 but also in all vertebrate groups from the lancelet to man. 



Hull Laborator\' of Anatomy. 



The ITiiiversity of Chicago, 



Feb. 4, 1909. 



