1 66 'Journal of Comparative Neurology and Psychology. 



Chemical irritability may prove to be more far-reaching and 

 fundamental in nervous excitation than is commonly recognized. 

 However this may be, two special reflex mechanisms have been 

 very elaborately difi'erentiated in vertebrates along quite diverse 

 lines for precise and rapid response to special external chemical 

 stimuli, the organs of smell and taste; and the explanation offered 

 in the preceding pages for the phylogenetic differentiation of these 

 two functional systems is not directly dependent upon any theory 

 regarding the ultimate nature of the primordial undifferentiated 

 sensory type from which they have sprung. 



Professor Parker concludes the note to which we have referred 

 with the remark, "From these experiments it is to be concluded 

 that the sense of taste in horn-pouts is complex and involves not 

 only the seventh nerve, but also the spinal nerves." Assent to 

 this proposition will be readily granted only if we define the sense 

 of taste in accordance with the "physical criterion" (see p. 157) as 

 Nagel does. In the opinion of the writer neither this criterion 

 nor the "anatomical criterion" (as I have used it on p. 159) alone 

 is adequate in the present state of our knowledge to serve as the 

 basis for generally acceptable definitions of all of the so-called 

 senses. Pending the extension of our knowledge in these fields, 

 fruitless controversy may be avoided by a clear recognition of the 

 fact that harmonious conclusions can be expected only on the 

 basis of an explicit understanding regarding the standpoint 

 chosen in every discussion. 



