ON THE CORPUSCULA TACTUS 287 



mode of termination ma)- be demonstrated in tlie papillae of the tongue 

 of the Frog, to which reference has been made above (fig. 6). Here 

 four or five coarse nerve-fibres enter the papilla, run to its very 

 extremity, become pointed, abruptly lose their fatty nature, and 

 terminate in the delicate reticulated fibres, which represent the elastic 

 element of the connective tissue of the part.^ 



4. Wagner, as we have seen, compares the corpuscles to the 

 Pacinian bodies, and I think with great justice. The Pacinian bodies 

 are, as is well known, principally found attached to the nerves of the 

 hand and foot in Man, to those of the mesentery in the cat, to the 

 nerves of the extremities of many animals, to those of the skin and 

 beak in birds, and to the intercostal nerves of the Boa constrictor. 

 They are commonly said to be composed of numerous corpuscles of 

 connective tissue, arranged concentrically, and separated by a clear 

 fluid. The innermost contains, besides this fluid, a nervous fibre, 

 which terminates in a free clavate or branched extremity. 



In the human hand, however, I have invariably found that this 

 description of their structure is not exactly correct. In fact, I find no 

 interspaces filled with fluid, nor any central cavity. If the body be 

 cut in two, each half remains as hard and uncollapsed as before ; if it 

 be torn, each layer of the " corpuscle " is seen to be united to its 

 neighbour by a delicate, transparent, more or less granular, or some- 

 times fibrillated substance. Again, the nerve lies not in a cavity, but 

 in a solid homogeneous substance ; and, so far as I have seen, termi- 

 nates more or less gradually in a portion of this mass, in which great 

 numbers of endoplasts (nuclei) lie, and which has thence almost the 

 appearance of cartilage.'' The structure of the rest of the body is, 



^ Much has been said as to the possibihty of confounding capillaries with nerves ; but I 

 conceive that such a mistake could hardly be made by any careful observer, unless perhaps 

 strong alkaline solutions had been allowed to act unwatched upon the preparation. I have 

 made use of both acetic acid and caustic soda, and I find the latter more available in 

 discovering nerves, the former in making out vessels and the general structure of the 

 papilla ; inasmuch as it renders their " nuclei " more obvious, while soda makes them 

 less so. It is very useful sometimes to use these re-agents alternately ; and it is a good rule 

 to apply them to the object only while under the microscope, so as to watch their gradual 

 operation. 



^ According to Will (Reichert's Report, p. 69, Mlill. Arch. 1851), the contents of the 

 central capsule of the Pacinian body in Birds is formed by a dense cellular mass, and 

 closely applied cells exist in the external neurilemma. From observations upon these bodies 

 in the Pigeon and Duck I can confirm this statement : in fact, the Pacinian bodies of the 

 birds are very like the young forms of those of Man. I have also noticed, as Wagner states 

 (1. u. p. 499), that the internal cellular mass is occasionally transversely striated, somewhat 

 like a tactile corpuscle. The Pacinian bodies in Birds are much more superficial than in Man, 

 being situated in the superficial layer of the corium, close to the sacs of the feathers. In the 

 Pigeon they are very small, frequently not more than i-i5oth — i-200th of an inch in their 



