Herrick, Organs of Smell and Taste. l6l 



Our argument thus far leads to an apparent impasse. The 

 physical and psychological criteria of smell and taste seem inade- 

 quate to account for the definite and fundamentally different 

 anatomical peculiarities of the organs in question. But we have 

 not yet considered the fourth line of evidence mentioned at the 

 beginning, that v^hich we called the physiological criterion; viz: 

 the characteristic responses normally following the stimulation of 

 these organs of sense. 



A suggestion made by Professor Sherrington in his recent 

 Lectures on the Integrative Function of the Nervous System seems 

 to me to put the matter in a perfectly clear light. As is well known, 

 Sherrington classifies the sense organs (receptors) into (i) extero- 

 ceptors, adapted for response to stimuh arising from without the 

 body; (2) proprioceptors, sense organs lying within the body 

 adapted to report to the central nervous system the physiological 

 state of the organs of somatic response themselves (typified by 

 muscle spindles, neuro-tendon organs, etc.); (3) interoceptors, 

 organs set to to guard the receptive surfaces of the body — enteron, 

 lungs, etc. Exteroceptors which are excited by stimuh arising at 

 a distance from the body are termed by Sherrington distance 

 receptors. 



The physiological analysis here outlined is full of helpful sug- 

 gestion in the morphology of the nervous system. Putting Sher- 

 rington's analysis into correlation with that of the new school of 

 functional morphologists, we recognize his first two types of recep- 

 tors as falling'within the somatic sensory group, for the chief organs 

 of response (effectors) in both cases are the somatic or skeletal 

 muscles. Sherrington's third type is the visceral sensory system, 

 caUing forth reflexes in the visceral musculature (including the 

 specialized striated visceral muscles of the branchial arches and 

 their derivatives in the higher vertebrates). 



The taste buds lying within the mouth of vertebrates are typical 

 interoceptors, and they with their nerves and cerebral centers are 

 classified as specialized visceral sensory organs. They are in 

 gnathostome vertebrates usually stimulated by food contained 

 within the mouth and the effectors with which they are most 

 directly connected are the visceral muscles of the jaws, gills, 

 oesophagus, etc. In the protochordate vertebrate ancestry it is 

 probable that there was but one chemical sense, and that feebly 

 developed; for these animals probably did not masticate their 



