342 



TERMINATION OF SENSORY NERVES. 



reader is referred for details regarding their distribution and variations, that cannot 

 be conveniently introduced here. 1 



The little bodies in question are, as already said, attached in numbers to the 

 branches of the nerves of the hand and foot (fig. 402), and here and there one or two 

 are found on other cutaneous nerves. They have been discovered also within the 

 abdomen on the nerves of the solar plexus, and they are nowhere more distinctly 





Fig. 402. A NERVE OP THE MIDDLE FINGER, WITH PACINIAN BODIES 



ATTACHED. NATURAL SIZE. (After Henle and Kb'lliker.) 



seen or more conveniently obtained for examination, than in 

 the mesentery of the cat, between the layers of which they 

 exist abundantly. They have been found on the pudic nerves 

 in the penis and clitoris, bulb of the urethra, and other parts, 

 on the intercostal nerves, sacral plexus, cutaneous nerves of the 

 upper arm and neck, nerves of the nipple and mammary gland, 

 and on the infra-orbital nerve. Lastly they have been recog- 

 nised on nerves to tendons and ligaments, and more rarely on 

 intra-muscular nerves, on the periosteal nerves, and, in con- 

 siderable numbers, on the nerves of the joints. In many 

 mammals they occur in masses of from 20 to 80 corpuscles 

 imbedded in the fat of the ball of the foot and also in the 

 interosseous space between the radius and ulna, and between 

 the tibia and fibula. They are found in individuals of 

 all ages. The figure of these corpuscles is oval, somewhat 

 like that of a grain of wheat, regularly oval in the cat, but mostly curved or 

 reniform in man, and sometimes a good deal distorted. Their mean size in the 

 adult is from T T T th to T Vth of an inch long, and from J g th to ^th of an inch broad. 

 They have a whitish, opaline aspect : in the cat's mesentery they are usually more 

 transparent, and then a white line may be distinguished in the centre. A slender 

 stalk or peduncle attaches the corpuscle to the branch of nerve with which it is 

 connected. The peduncle contains a single medullated nerve-fibre ensheathed in 

 perineurium, with connective tissue and one or more fine blood-vessels ; it joins the 

 corpuscle at or near one end, and conducts the nerve-fibre into it. The little body 

 itself, examined under the microscope, is found to have a distinct lamellar structure 

 (fig. 403). It consists, in fact, of numerous concentric membranous tunics 

 encasing each other like the coats of an onion. Surrounded by these tunics, and 

 occupying a cylindrical space in the middle of the corpuscle, is the core, formed of 

 transparent and seemingly homogeneous soft substance, in the midst of which the 

 prolongation of the nerve-fibre is contained. The number of tunics is various ; 

 from forty to sixty may be counted in large corpuscles. Those which are situated 

 next to the central or median cavity, and comprehending about half of the entire 

 number, are thinner and closer together than the more exterior ones, seeming to 

 form a system by themselves, which gives rise to a white streak often distinguish- 

 able along the middle of the corpuscles when seen on a dark ground. Outside of 

 all, the corpuscle has a coating of ordinary connective tissue. 



The lamellae or tunics correspond very closely in structure to the lamellae of the 



1 A complete list of papers which had appeared up to 1880 on this subject (and, indeed, not only on 

 the Pacinian corpuscles, but on all the several kinds of terminal corpuscles and other sensory nerve- 

 endings) will be found in a monograph by Prof. Fr. Merkel, "Ueber die Endigungen der sensiblen 

 Nerven in der Haut der Wirbelthiere." Rostock, 1880. A concise resume and classification of the 

 sensory end- organs, by Prof. W. Krause, will be found in the "Biologisches Centralblatt,"May and June, 

 1884. 



