334 HOW TO WORK 



unstriped muscular fibre will be understood if fig. 388, pi. LXII, be 

 referred to. This is a drawing of a portion of some of the muscular 

 fibre cells from the bladder of the frog, amongst which the finest 

 ramifications of the nerve fibres are well seen. These nerve fibres 

 form bundles and networks, having wide meshes in which the fine 

 muscular fibres lie. Some of the muscular fibres are spindle-shaped, 

 while others consist of three fibres radiating from a triangular central 

 portion. It is obvious from the arrangement figured that the nerve 

 fibres only influence the contractile fibre indirectly, for they are not 

 anywhere in actual contact with the contracting material of the fibre, 

 nor in any case can an end organ or any form of terminal apparatus 

 be detected, nor are the nerves connected with the nucleus or with 

 any part of the muscular tissue itself. 



391. Nerve Fibres distributed to Organs of Special and General 

 Sensation. The ultimate arrangement of purely sensitive nerve fibres 

 may be demonstrated in many of the terminal organs of man, and the 

 lower animals, such as the papillae of the skin and mucous mem- 

 brane in certain localities ; but of all the organs studied by micro- 

 scopists perhaps the larger papillae (the fungiform papillae) of the 

 frog's tongue are the most beautiful as well as the most convenient, 

 not only for investigating the terminal distribution of purely sensitive 

 nerve fibres and for demonstrating the essential structure of a highly 

 sensitive organ, but for ascertaining the relations and connections 

 which nerve fibres exhibiting different functions, have with one 

 another. 



In the small portion of tissue constituting one of these papilla? 

 we see striped muscular fibres, capillary vessels, purely sensitive 

 nerve fibres forming an expanded terminal plexus or network at the 

 summit of the papilla, motor nerve fibres distributed to the muscle, 

 nerve fibres around the capillary vessel, and a few very fine nerve 

 fibres ramifying in different parts of the papilla. All these are 

 embedded in and held together by connective tissue, forming the 

 body of the papilla, the summit of which is surmounted by a peculiar 

 epithelium-like tissue, perhaps connected with the nerves and 

 belonging to nerve texture, while its sides are covered with ordinary 

 ciliated epithelium. 



These papillae have been studied by numerous observers, and, 

 strangely enough, the latest writer has seen far less than many 

 of his predecessors, probably because he has been less successful in 

 preparing his specimens. Fig. 390 is a copy of Hartmann's figure 

 taken from pi. XVIII, Miiller's Archiv, 1863. It represents the mode 

 of termination of the bundle of nerve fibres in the papilla according to 

 this observer. It would probably be difficult to adduce a more striking 



