288 ox THE CORPUSCULA TACTUS 



essentially, the same,'' and the appearance of their concentric 

 capsules is produced by the arrangement of their endoplasts in 

 concentric layers in the outer part of the Pacinian body, and their 

 connexion by the laminas and fibres of more or less imperfect elastic 

 substance. 



The concentric lines in the Pacinian bodies are no more evidence 

 that they are composed of capsules, than the parallel lines in the 

 neurilemma of small nervous twigs (fig. 7) are evidence that it is com- 

 posed of concentric tubes. In each case the appearances depend 

 simply upon the disposition of the lines of elastic tissue. In fact, the 

 Pacinian bodies are nothing more than thickened processes of the 

 neurilemma of the nerve to which they are attached ; and differ from 

 the " tactile corpuscles " only in the circumstance that the thickening 

 takes place on each side of the nerve fibril, while in the Pacinian body 

 it takes place on both sides. The difference in the direction of the 

 apparent layers is not so great as it seems, since, at each extremity of 

 the Pacinian body, these are, as in the tactile corpuscle, perpendicular 

 to the direction of the nerve. 



5. The evidence with respect to the physiological functions of 

 either the corpiiscula tacUis or of the Pacinian bodies is wholly nega- 

 tive ; and it seems useless to enter upon the region of hypothetical 

 suppositions. But I think that Comparative Anatomy promises to 

 offer some assistance in this case by showing that these structures 

 form the lowest terms, in a series whose higher members attain a very 

 great development in certain animals, though their precise function is 

 in many cases obscure. The homology of the tactile corpuscles with 

 the Pacinian bodies appears, from what has been said, to be clear 

 What are the Pacinian bodies ? Mr. Bowman, in his article on this 

 subject in the Cyclopaedia of Anatomy, will not decide upon their 

 function, but points out their close similarity to certain bodies de- 

 scribed by Savi in the Torpedo, and subsequently more fully described 

 by Leydig (Beitrage zur Anat. d. Rochen. u. Haie.). These are 

 capsules of homogeneous connective tissue, containing a semi-solid 

 gelatinous substance, and inclosing a knob-like process ; the termina- 



long diameter, and possess only one or two " capsules," with ^ proportionally large inner 

 mass. In the Duck they are to be met with in great numbers in the skin of the beak, especially 

 in the ridged portion at its edges. Here the Pacinian bodies, often very small (i -400th of 

 an inch), lie immediately under the epidermis, with their long diameters more or less parallel 

 to the surface ; and the nerves are related to them, just in the same manner as those of the 

 fingers are to the tactile corpuscle. It is difficult to suppose that they have not here some 

 special reference to the sense of touch. 



' Compare Strahl. Mull. Archiv, 1848, who gives a similar account of the structure of the 

 layers. 



