PACIXIAN BODIES. 



cliii 



Fig. LXXXIX. 



papers by "W. Krause* and Engelmann,f the reader is referred for details that cannot 

 be conveniently introduced here. 



The little bodies in question (fig. LXXXIX) are, as already said, attached in great 

 numbers to the branches of the nerves of the hand and foot, 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 seen 

 or more conveniently obtained for examination, than in 

 the mesentery and omentum of the cat. between the layers 

 of which they exist abundantly. They have been found on 

 the pudic nerves in the glans penis and bulb of the urethra, 

 on the intercostal nerves, sacral plexus, cutaneous nerves 

 of the upper arm and neck, and on the infraorbital nerve. 

 Lately they have been recognised on the periosteal nerves, 

 and, in considerable numbers, on the nerves of the joints. 

 They are found in the foetus, and 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 dis- 

 torted. Their mean size in the adult is from i to i 

 of an inch long, and from i to i of an inch broad. 

 They have a whitish, opaliae aspect : in the cat's mesen- 

 tery 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 tubular nerve-fibre ensheathed in filamentous con- 

 nective tissue, with one or more fine blood-vessels ; and 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 beautiful lamellar struc- 

 ture (fig. xc, A). It consists, in fact, of numerous concen- 

 tric membranous capsules incasing each other like the 

 coats of an onion, with a small quantity of pellucid fluid 

 included between them. Surrounded by these capsules, and 



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

 transparent and homogeneous soft substance, in the midst of which the prolonga- 

 tion of the nerve-fibre is contained. The number of capsules is various ; from forty 

 to sixty may be counted in large corpuscles. The series immediately following the 

 central or median cavity, and comprehending about half of the entire number, are 

 closer together than the more exterior ones, seeming to form a system by themselves, 

 which gives rise to a white streak often distinguishable by the eye 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 capsules, at least the more superficial 

 ones, consist each of an internal layer of longitudinal and an external of circular 

 fibres, which resemble the white fibres of areolar and fibrous tissue, with cell-nuclei 

 attached here and there on the inner layer, and a few branched fibres of the yellow or 

 elastic kind running on the outer. The nerve-fibre, conducted along the centre of the 

 stalk, enters the corpuscle, and passes straight into the central cavity, at the further 

 end of which it terminates. 



The fibrous neurilemma surrounding the nerve-fibre in the peduncle accom- 

 panies it also in its passage through the series of capsules, gradually decreasing 

 in thickness as it proceeds, and ceasing altogether when the nerve has reached the 

 central cavity. According to Pacini, with whom Eeichert agrees in this particular, 

 the neurilemma forms a series of concentric cylindrical layers, which successively 

 become continuous with, or rather expand into the capsules, the innermost, of 

 course, advancing farthest. Others suppose that the capsules are all successively- 

 perforated by a conical channel which gives passage to the nerve with its neuri- 



* Anat. Untersuchungen ; Hanover, 1861, and Zeits. f. rat. Med. xvii. 1805. 

 t Zeits. f. Wiss. Zool. xiii. 1863. 



Fig. LXXXIX. A 

 NERVE OF THE MIDDLE 

 FINGER, WITH PACINIAN 



BODIES ATTACHED. NA- 

 TURAL SIZE (after Henle 

 and Kolliker). 



