CRANIAL NERVES 145 



proprioceptive system and the faulty connotations of the term in 

 present usage, it might be better to avoid the word hereafter and 

 replace it by the more inclusive name, "proprius system." 



The preceding comments on the proprioceptive system apply, 

 mutatis mutandis, to Sherrington's exteroceptive and interoceptive 

 systems also. In his original definitions of these terms, Sir Charles 

 was careful to insist that each component of each of these three 

 subdivisions of the total pattern of behavior must be viewed in its 

 entirety as a unitary act and that the significance of these acts can 

 be understood only in terms of their reciprocal relationships with one 

 another and with the total action system of the animal. The critical 

 feature of each of these acts is the end-result, the actual behavior 

 exhibited. The names originally given to these three classes of func- 

 tions put the emphasis on the receptive organs, w^here it does not 

 belong. Some obscurity and confusion may be avoided if the unity of 

 these several components of behavior is recognized in their nomen- 

 clature. The exteroceptive systems, viewed in their entirety, are 

 somatic, the interoceptive systems are visceral, and the proprioceptive 

 systems are ancillary to all muscular activity and, accordingly, may 

 be termed proprius. Sherrington's terms, "exteroceptors," "intero- 

 ceptors," and "proprioceptors" are suitable names for the receptive 

 organs, with the qualification that the same organ may, on occasion, 

 activate somatic, visceral, or proprius responses. 



VISCERAL SENSORY AND GUSTATORY NERVE ROOTS 



General visceral sensory fibers of wide peripheral distribution 

 enter the brain by the vagus roots, and the IX and VII roots contain 

 smaller numbers of similar fibers from the mucous surfaces of the 

 mouth and pharynx. Taste buds are widely distributed in these 

 mucous surfaces, and the gustatory fibers are indistinguishably 

 mingled with the general visceral fibers peripherally in the roots of 

 the VII, IX, and X nerves and centrally in the f . solitarius, more of 

 them entering the brain anteriorly than posteriorly. This mixed 

 group of peripheral fibers, as a whole, is quite distinct from all other 

 functional systems and it was termed by the earlier students of nerve 

 components in lower vertebrates the "communis system" because all 

 its fibers converge into a single central bundle, the f. communis 

 (Osborn, '88). This we now know is homologous with the mammalian 

 f. solitarius. The peripheral and central arrangements of the chemo- 

 receptors illustrate some general principles which will next be ex- 

 amined. 



