412 SPECIAL HISTOLOGY. 



most part undulating, upon which circumstance their transversely banded 

 aspect depends ; they exhibit, howeyer, in their course, very frequent 

 anastomoses, in which way the various larger and smaller plexuses with 

 decussating fibres are formed. The formation of these plexuses is due 

 to an interchange of entire fasciculi or fibres, never to a connection be- 

 tween the individual primitive fibres, and in a microscopical point of 

 view affords no point worthy of remark. 



Divisions of the nerve-fibres do not occur, according to our present 

 experience, in the trunks and larger branches of the spinal nerves of the 

 Mammalia [in Fishes, Stannius noticed numerous divisions in the trunks 

 of the motor and mixed nerves (" Archiv fur phys.," Heilk. 1850, p. 

 77)], nor do they exhibit any considerable change in their diameter ; 

 but in the ultimate ramifications, on the other hand, it is certain that 

 such divisions do take place, even in Man, accompanied by a very con- 

 siderable diminution in the size of the fibres ;* with respect to which con- 

 ditions, and the terminations in the skin, muscles, bones, and membranes 

 in general, reference may be made to the detailed descriptions given in 

 the proper places. 



One kind, only, of termination of the spinal nerves, is still to be 

 noticed here, that in the Pacinian bodies. The small bodies, so named 

 by Henle and myself (" Ueber die Pacin. Korperchen des Menschen und 

 der Thiere," Zurich, 1844), were first accurately described by the Italian, 

 Pacini ("Nuovi organi scoperti nel corpo umano," Pistoja, 1840), espe- 

 cially in the nerves of the palm of the hand and sole of the foot, and, 

 in fact, as Langer of Vienna afterwards showed, had been previously 

 noticed by A. Vater (J.G. Lehmann, " De consensu partium corp. hum.," 

 Vitembergse, 1741), although their nature had not been recognized. 

 These organs are of an elliptical or pyriform shape, of a whitish trans- 

 parent color, with whiter streaks internally, and measure J-2 lines in 

 size ; in Man, they are constantly found on the cutaneous nerves of the 

 palm of the hand and sole of the foot, in the subcutaneous connective 

 tissue itself, and most numerously in the fingers and toes, particularly 

 on the third phalanx, according to Herbst ("Die Pacin. Korperchen 

 und ihre Bedeutung," Gott., 1847), there are about 600 in the hand and 

 not quite so many in the foot; besides which, it must here also be 

 stated, that they are invariably found on the great sympathetic plexus, 

 in front of, and close to the abdominal aorta, behind the peritoneum, 

 particularly near the pancreas, frequently also in the mesentery, close 

 to the intestine ; and also occasionally on other nerves, such as the 



* [The ultimate ramifications are supposed by Axmann (1. c.), to be merely axis-cylinders 

 surrounded by the sheaths of the nerves, the granular contents of the nerve-tubes having 

 gradually disappeared. DaC.] 



