BY DR. KLEIN. 89 



SECTION III. PERIPHERAL NERVE ENDINGS. 



Terminal Organs of Nerve Fibres. Pacinian Bod- 

 ies. The Pacinian bodies are oval or pear-shaped little mus- 

 ses which are found in the subcutaneous tissue of the skin of 

 the finger, and in that of the beak and tongue in birds (goose 

 and duck). In man they are met with also in the genital tract, 

 e. </., in the labia majora, prostate, and corpora cavcrnosa : in 

 all these situations they can be best studied in sections. They 

 are most easily demonstrated, however, in the mesentery of 

 the cat, in which they are visible to the naked eye as elliptical, 

 transparent bodies, occurring mostly in the fatty parts. Pre- 

 parations are made as follows : A mesentery of a cat that 

 has just been killed is spread out on an object-glass and cov- 

 ered with a drop of serum or half per cent, solution of common 

 salt; or a portion of mesentery containing Pacinian bodies is 

 placed in solution of bichromate of potash for twenty-four 

 hours, and then covered in glycerine. We begin our study 

 with the medullated nerve fibre, which enters the corpuscle at 

 one end. From the point at which the nerve parts from the 

 twig from which it is a branch, its course is winding. As it 

 approaches the Pacinian body its sheath becomes thicker, and 

 acquires an appearance as if it consisted of several layers of 

 nucleated membrane. The dark-bordered nerve fibre is sepa- 

 rated from the sheath by a distinct, clear interspace, into 

 which oblong nuclei project at regular distances from the in- 

 ternal surface of the sheath, so as to resemble an endothelium. 

 The Pacinian corpuscle may be divided into the neck (the 

 point at which the nerve enters) and the body. In the neck, 

 the lamellae of the Schwann's sheath split repeatedly, becom- 

 ing further and further apart from each other, so as to form 

 the well-known concentric capsuler of which the body is con- 

 stituted. Each capsule is beset with regularly arranged flat 

 oblong nuclei ; and, in the part of the body which is nearest 

 the neck, each capsule communicates with its neighbors by 

 cross lamellae, which run obliquely from one to the other. 

 Elsewhere the capsules are discontinuous. In the neck, the 

 nerve fibre is dark-bordered and convoluted, but as it enters 

 the clear space which is contained in the inmost capsule it 

 becomes straight, and at the same time pale and finely streaked. 

 In its course in the axis of this space it is separated from the 

 capsule by a clear interval, into which nuclei, arranged at 

 regular distances, project. Near the end of the axial space 

 the nerve fibre usually divides into two, occasionally into 

 three, branches, each of which ends in a pear-shaped enlarge- 

 ment (cell), containing a vesicular nucleus. Sometimes the 

 nerve fibre remains undivided, in which case the terminal cell 

 is relatively larger. In the mesentery of the cat I have seen 



