TISSUES OF THE BODY. 331 



These two observers gave the corpuscles the name of Pacinian bodies, without any 

 idea of their previous discovery by Vater. This name has been retained by some, 

 while by others the structures are designated as Vater- Pacinian corpuscles. 



187. 



Having finished the consideration of these terminal bodies, let us now 

 turn to the question as to how the remaining wholly sensible nerves end, 

 one of the most obscure subjects in minute nervous anatomy, and one 

 about which much uncertainty still prevails. 



It is quite obvious that centripetal nerves must occur in voluntary 

 muscle as recipients of muscular sensation. Our acquaintance, however, 

 with them, is still very slight. 



With a view to throwing some light on this point, the platysma of the 

 frog was subjected by Kodliker to minute investigation, being peculiarly 

 well suited for this purpose. Here there is to be seen possibly springing 

 from the division of a single broad nerve tube a slight nervous ramifica- 

 tion, confining itself almost entirely to the anterior surface of the muscle. 

 The narrow nervous twigs of the same are, at their commencement, still 

 dark-edged, but become paler as the branching progresses, and are seen 

 later on as fibrils clothed with a loose neurilemma studded with nuclei. 

 Eventually they terminate, after the loss of this envelope, in the form of 

 extremely fine still branching filaments. The latter measure less than 

 0'0023 mm. in diameter. At intervals in their course, as well as at the 

 nodal points of their division, small structures like nuclei are to be 

 observed. Eetiform connections among the fibres appear to occur only 

 as exceptions. 



In connection with other nerves, however, to which a sensory nature 

 may be ascribed with greater or less probability, terminal networks of 

 various kinds, formed of pale fibres, have been described. Arnold the 

 younger, for instance, mentions such an one on the surface of the con- 

 junctival mucous membrane, and Billroth another on the mucous 

 membrane of the pharynx of the water salamander. Again, Koelliker 

 speaks of one in the mucous membrane of the small intestine of the frog, 

 and confirms Billrotli's statements as regards the pharynx of the last- 

 mentioned animal. 



Similar terminal networks of pale fibres have also been described by 

 Axmann and Ciaccio as occurring in the cutis of the frog, and, many 

 years ago, as existing in the tail of the tadpole. Klein has also met with 

 the same networks, and described them as occurring very widely 

 throughout the body of the same animal. 



For many years past we have known of certain isolated instances of 

 their occurrence in the skin of mammals, and ScJicll has recently demon- 

 strated their presence here in great abundance. 



There can be no longer any doubt that the most superficial termina- 

 tions of sensible nerves frequently penetrate into the epithelial layers of 

 their organs. 



But their ultimate arrangement is still very variously explained. The 

 fact is, that at the present time our modes of investigation are still too 

 imperfect to admit of our settling the matter conclusively. 



Some suppose them to end in a terminal plexus, so that we would only 

 have an intermixture simply of epithelial cells and nerve fibres. Others, 

 again, state that the latter penetrate into the cells and end in the nucleoli. 

 Thirdly, many support the view that there exist certain peculiar 



