TISSUES OF THE BODY. 



329 



Fie. 316 Two human tactile papillae from the 

 velar surface of the index finger. In the interior 

 we have the tactile corpuscles, into whose tissue 

 the nervous fibres may be seen entering. 



sently. They communicate to the whole structure a characteristic trans- 

 versely striated appearance. 



The nerve fibres (fig. 316) pass out towards these bodies either singly, 

 or, as is more frequently the 

 case, double : at times, also, 

 they are trebled or quadrupled. 

 They are enveloped in simple neu- 

 rilemma (fig. 316), which is con- 

 tinuous with the capsule. They 

 are dark-edged, 0'0045 mm. and 

 less in breadth, and enter the base 

 of the touch-corpuscle, or at times 

 also its side. 



The mode in which they end, 

 however, is difficult to determine. 

 At limes a peculiar twining of the 

 nerve tubes around the tactile cor- 

 puscle may be remarked, or they 

 may be seen to run for a greater or 

 less distance straight along the 

 latter. They all finally pass into the 

 interior of the corpuscle, however, 

 but in what manner they end there 

 is still unascertained. In all probability they spread out in the form of pale 

 non-medullated fibres or axis cylinders, like those of the terminal bulb. 

 That the transversely arranged nuclear bodies, already mentioned, are con- 

 nected with the termination of the fibrillse appears extremely improbable. 



186. 



We turn now, in conclusion, to the Pacinian bodies, which may be 

 likened to a terminal bulb enveloped in numerous concentric capsules of 

 connective-tissue. 



As they come under our notice they are elliptical structures, sometimes 

 more elongated than at others, and measuring from 1 to 2 mm. in length. 

 To the unaided eye they appear translucent, and marked towards the 

 axis with a streak. In man they occur regularly on the nerves supplying 

 the palm of the hand and sole of the foot, but with especial frequency on 

 those passing to the tops of the fingers and toes. Their total number, in 

 these parts taken together, has been estimated at from 600 to 1400. 

 According to Rauber, they are met with also, but with less frequency and 

 constancy, at many other points in the body : thus on the dorsum of the 

 foot and back of the hand, beneath the skin of the arm, forearm, and 

 neck ; on the intercostal nerves, and all the articular nerves of the extre- 

 mities. They are likewise to be found on many nerves supplying bone, 

 and in the interior of the muscles of the hand and foot ; further, in the 

 nerves of the parts of generation, and finally on the plexuses of the sym- 

 pathetic system, round about the abdominal aorta. Again, they are 

 encountered among the mammalia ; especially on the sole of the foot, and 

 with exquisite distinctness, and in greater or less number, in the mesentery 

 of the cat. Pacinian bodies are also found in birds as well as in mammals, 

 although modified to a certain extent. 



The laminae of the capsules are looked upon as formed of connective- 

 tissue, consisting of an either homogeneous or somewhat fibrillated 



