PACINIAN CORPUSCLES are very remarkable structures appended to the nerves. i In the human subject they are found in great numbers in connection with the nerves of the hand and foot, and sparingly on other spinahnerves, and on the plexuses of the sym pathetic, but never on nerves of motion. They always present a pro.riimil end, attached to the nerves by a stalk of fibrous tissue prolonged from the neurilemma, and occasion ally one-tenth of an inch long; and a distal end, lying free in the connective or areolar tissue. In the human subject the corpuscles vary in length from one-twentieth 10 one tenth of an inch. They are usually seen very readily in the mesentery of the cat, appearing as pellucid oval grains, rather smaller than hemp-seed. The microscopic examination of these bodies discloses an internal structure of a very remarkable kind. They consist, first, of a series of membranous capsules, from 30 to 60 or more in number, inclosed one within the other; and secondly, of a single nervous fiber, of the tubular kind, inclosed in the stalk, and advancing to the central capsule, which it traverses from beginning to end, and where it finally termivates in a fixed swollen extremity. The 10 or 15 innermost capsules are in contact with one another, while the rest arc separated by a clear space containing fluid, which is so abundant as to constitute far the largest por tion of the bulk of the entire corpuscle. Such are the views of Pacini (as given in his
Icvoxi Organi Scoperte earl CorpoUnman, 1840), who is usually regarded as their discoverer, although they had been noticed and roughly described nearly a century before by Voter, of Henle, and of Todd and Bowman; but later observations made by Huxley, Leydig, K6Iliker, and others, show that the question of their true nature is stiil an open one. Huxley asserts that their central portion is solid, and not hollow; that in birds, and in the human hand, there is no fluid between the laminae—and indeed, that the lamime themselves have no real existence—the Pacinian corpuscle being merely a solid mass of connective tissue (a thickened process of the neurilemma of the nerve to which it is attached), whose apparent lamination depends on the regular disposition of its elastic elements. If Pacini 's views of these structures he correct, there is probably some gen eral analogy between the electric organs of the torpedo and those corpuscles; at present we know nothing with certainty regarding their office.