PACINIAN BODIES. 



877 



process of the fibrous neurilemma, advances 

 right into the centre of a series of concentric 

 ovoidal capsules of fibrous membrane, through 

 a channel which perforates them all, and which 

 has its proper wall, to which every capsule is 

 attached. All the capsules, except from five to 

 twenty of the inner ones, have spaces between 

 them containing a clear watery fluid. These 

 spaces do not communicate with one another 

 or with the channel in which the nerve runs. 

 Each one is distended by its own fluid, and in 

 the natural state is more or less tense, offering 



Fig. 482. 



Pacinian corpuscle, from the mesentery of 'a cat ; in- 

 tended to shew the general construction of these 

 bodies. The stalk and hody, the miter and the inner, 

 system of capsules, with the central cavity, arc seen, 



a. Arterial twig, ending in capillaries, which 

 form loops in some of the intercapsular spaces, 

 and one penetrates to the central capsule, b. 

 The fibrous tissue of the stalk, prolonged from 

 the neurilemma. n. Nerve-tube advancing to the 

 cential capsule, there losing its white substance, 

 and stretching along the axis to the opposite end, 

 where it is fixed by a tubercular enlargement. 

 from Todd and Bowman. 



resistance to external pressure. The innermost 

 capsule of all is an elongated nearly cylindrical 

 cavity, somewhat larger at the further end, and 

 always contains a clear fluid, which distends it 

 and prevents its sides from falling together. 

 The nerve-tube has the ordinary double dark 

 contour as well as every other character of 

 those found in the ordinary cerebro-spinal 

 fibres until its entry into the central capsule. 

 At that point it becomes less bulky, somewhat 



flattened (so that its section is oval instead of 

 round), and in particular much paler. The 

 dark border which has distinguished it hitherto 

 now disappears, and if it were not for the trans- 

 parency of the contents of the capsules its fur- 

 ther course would be untraceable. It is, how- 

 ever, when fresh, and with a good light, dis- 

 tinctly seen to proceed along the very axis of 

 the central capsule from one end to the other, 

 and finally to be implanted by more or less of 

 a swelling (Jig. 483) into the further extremity 



Fig. 483. 



Extremity of the pale nerve-fibre in the inner capsule 

 of a Pacinian body from the mesentery of a cat. 



n, pale fibre advancing into the further end of 

 the central capsule ; a, conical swelling by which 

 the nerve is fixed ; b, corpuscle of the inner cap- 

 sule ; c, capsules of the internal system. Magni- 

 fied 300 diameters. From Henle and Kolliker. 



of this central compartment. The originally 

 dark border of the nerve-tube does not cease 

 with absolute abruptness, but the two lines of 

 the border coalesce in a somewhat sloping 

 manner, and the pale continuation has merely 

 a single bounding line, and that so exceedingly 

 thin as not to allow of being described as an 

 investment distinct from the rest of the fibre. 

 This line, as Henle and Kolliker have re- 

 marked, is more evident when the edge of the 

 flattened fibre is towards the observer than 

 when the flat surface is upwards, in which 

 latter position it is sometimes altogether absent. 

 Such is the general plan of the structure of 

 these bodies. Their usual length is from l-20th 

 to 1-1 Oth of an inch, and their stalk is often 

 l-10th of an inch long. Though usually oval, 

 they are often more or less elongated and bent 

 on themselves. Sometimes the internal cap- 

 sules only are bent, while the outermost are 

 simply oval. In the human subject they are 

 found in large numbers, detached or in clus- 

 ters, in the subcutaneous areolar and adipose 

 tissues of the palm and sole, in connection 

 with the cutaneous nerves, as well as more 

 sparingly in the same connection at other parts 

 of the extremities. A few are also met with in 

 the sympathetic plexuses ; and in the cat in par- 

 ticular they are usually so abundant in the 

 mesentery and omentum, as instantly to arrest 

 the eve when these parts are spread before it. 

 They are here indeed most favourably situated 

 for examination. They are included merely 

 between the duplicature of the transparent peri- 

 toneum, can be obtained in great numbers per- 

 fectly fiesh,and admit of being inspected with- 

 out the addition of any water or other medium. 



