514 NERVOUS SYSTEM. 



ties, the nerves beneath the mammary glands, the nerves of the nipples, and 

 in the substance of the muscles of the hands and feet. They are found with- 

 - out exception on all of the great plexuses of the sympathetic system, in front 

 of and by the sides of the abdominal aorta, and behind the peritoneum, par- 

 ticularly in the vicinity of the pancreas. They some- 

 times exist in the mesentery and have been observed near 

 the coccygeal gland. 



The corpuscles consist simply of several layers of 

 connective tissue enclosing one, two or three central 

 bulbs in which are found the ends of the nerve. These 

 bulbs are finely granular and nucleated, and are regarded 

 by most anatomists as composed of connective tissue. 

 At the base of the corpuscle, is a pedicle formed of con- 

 nective tissue surrounding a medullated nerve - fibre 

 which penetrates the corpuscle. Within the corpuscle 

 the medullary substance of the nerve-fibre is lost and 

 only the axis-cylinder remains. 



The situation of these corpuscles, beneath the true 

 skin instead of in its substance, shows that they can not 

 be properly considered as tactile corpuscles, a name 

 which is applied to other structures found in the papilla 



. rjr j . -11, 



or the conum ; and it is impossible to assign to them any 

 special use connected with sensation, such as the appre- 

 ciation of temperature, pressure or weight. All that can 

 be said with regard to them is that they constitute one of 



nerve V2e?ve?wiiich tne sey eral modes of termination of the nerves of gen- 

 has lost its medullary m . Q l oa-nail-il if XT- 

 substance and sheath; eial sensibility. 



Tactile Corpusdes.The name tactile corpuscles im- 

 P^ es that t ^ iese bodies are connected with the sense of 

 touch ; and this view is sustained by the fact that they 

 are found almost exclusively in parts endowed to a marked degree with 

 tactile sensibility. They are sometimes called the corpuscles of Meissner 

 and Wagner, after the anatomists by whom they were first described. The 

 true, tactile corpuscles are found in greatest number on the palmar sur- 

 faces of the hands and fingers and the plantar surfaces of the feet and toes. 

 They exist, also, in the skin on the backs of the hands and feet, the nipples, 

 and a few on the anterior surface of the forearm. The largest papillae of the 

 skin are found on the hands, feet and nipples, precisely where the tactile 

 corpuscles are most abundant. Corpuscles do not exist in all papillae, and 

 they are found chiefly in those called compound. In an area a little more 

 than ^g of an inch square (2'2 mm. square), on the third phalanx of the in- 

 dex-finger, Meissner counted four hundred papillae, in one hundred and eight 

 of which he found tactile corpuscles, or about one in four. In an equal area 

 on the second phalanx, he found forty corpuscles ; on the first phalanx, fif- 

 teen ; eight on the skin of the hypothenar eminence ; thirty-four on the 

 plantar surface of the ungual phalanx of the great-toe ; and seven or eight in 



FIG. 179. - Corpuscle 



Vater (Sappey). 



