Herrick, Organs of Snie/l and Taste. 165 



of the original phylogenetic differentiation was determned and 

 that this is still the dominant feature of the two systems in ques- 

 tion. 



The conclusion is that the agencies which acted to produce 

 the differentiation from each other of the senses of smell and 

 taste are not to be sought primarily in the stimuli calling forth 

 the reflexes, but rather in the character of the response evoked 

 by the stimulus. 



Addendum. As these pages pass through the press an abstract 

 of the very interesting experiments of Parker appears in the Pro- 

 ceedings of the American Society of Zoologists {Science, n. s., vol. 

 27, no. 690, March 20, 1908, p. 453). Parker has previously 

 determined that the skin of the body of the frog and of various 

 other aquatic animals is sensitive to chemical stimuli. Quite in 

 accord with those results, he now finds that the same is true for 

 the common fresh water catfish, Ameiurus. This fish possesses 

 taste buds innervated by the nervus facialis scattered in the skin 

 over practically the whole body surface. If the nerves supplying 

 these taste buds on the trunk are cut, the fish no longer reacts to 

 a bait in the normal way (by turning to snap at the bait) when it is 

 presented to the flank of the body. Nevertheless such operated 

 fishes are sensitive to sour, saline and alkaline solutions when 

 applied to the skin of the trunk. 



These results, together with the control experiments described, 

 demonstrate that the spinal nerves of this teleost, hke those of 

 the frog, are sensitive to certain external chemical stimuli. The 

 important question at once arises, are these responses to chemical 

 stimulation of the spinal nerves transmitted by the same nerve 

 fibers which transmit the tactile stimuli, or by some other compo- 

 nent of the spinal nerves ? We know from abundant physiological 

 and clinical experience that the cutaneous rami of the spinal 

 nerves of man transmit impulses which are perceived introspec- 

 tively as very diverse sensation qualities (touch, temperature, etc.). 

 There is evidence that some at least of the different functions of 

 the sensory spinal nerves are served by anatomically different 

 neurone systems; but whether the ability to respond to direct 

 peripheral chemical stimulation is limited to one or more of these 

 systems or common to all of them, further experiment alone can 

 determine. 



