342 



OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



separately, or all together, 1 Ed.~\; but in the tail of the Tadpole, as also in the 

 mesentery of the Amphibia, it was first observed by Schwann, 2 and has been since 

 confirmed by Dr. Sharpey, 3 that the ordinary primitive nerve-fibres, after separat- 

 ing from the fasciculi, divide into fibrils of much smaller size, bearing a strong 

 resemblance to the "gelatinous" kind, which spread out in various directions, and 

 form a plexus not unlike that of the capillaries. The origin of these plexuses has 

 been traced by Prof. Kolliker; 4 who has found that they formed, like capillary 

 plexuses ( 294), by the inosculation of the prolongations of radiating cells, 

 whose centres are at a considerable distance from each other. Looped termina- 

 tions may be seen in the nerves supplying the dental sacculi (Fig. 112), and in 



those of the conical papillae of the tongue; 



Fig. 112. on the other hand, in the fungiform papillae 



of the tongue, the Author, after a very at- 

 tentive search for them (in conjunction with 

 Messrs. Bowman, Kiernan, and T. Whar- 

 ton Jones), could not succeed in distinguish- 

 ing them; no free extremities, however, 

 were discernible; and some appearances 

 were seen, which indicated that the axis- 

 band is here also prolonged beyond its en- 

 velops, and is continued as a gelatinous 

 fibre into the tissue at the apex of the pa- 

 pilla, where it ceases to be distinguishable. 

 It will hereafter be shown that, in the 

 Retina, in some parts of the internal Ear, 

 and perhaps also on the Olfactory surface, 

 the peripheral fibres come into relation with 

 true ganglionic cells; and it may be ques- 

 tioned whether it be not as requisite for the 

 reception of any other kind of sensory im- 

 pressions than those of a mere mechanical 

 nature, that a ganglionic vesicle, or its equiv- 

 alent under some other aspect, should be in 

 connection with the peripheral expansions of 

 the sensory nerves, as it is for the origination 

 of motor impulses, that ganglionic vesicles 

 should be in relation with them in the cen- 

 tral organs. 



344. One very peculiar mode of termination of certain of the Nervous fibres, 

 the physiological import of which, however, is entirely unknown, is in the bodies 

 termed Pacinian, after Pacini, the first writer who gave an account of their 

 internal structure, and demonstrated their essential connection with the nervous 

 fibres. His researches have been followed up by Henle and Kblliker, 5 and also 

 by Mr. Bowman. 8 These bodies are found in considerable numbers attached to 

 the branches of the nerves of the hand and foot, as they pass through the sub- 

 cutaneous fat in their way to the skin (Fig. 113, B) ; they are also occasionally 

 met with on subcutaneous nerves elsewhere, and they have been discovered on 

 the nerves of the solar plexus in the abdominal cavity. Their form usually 

 approaches to the oval, though they are generally more or less curved or reni- 



1 "Brit, and For. Med. Chir. Rev.," from "Gaz. Med.," Mars 6. 



2 " Medizinischen Zeitung," Aug., 1837. 



3 Introduction to "Quain's Elements," vol. ii. p. 169, Am. Ed. 



4 "Annales des Sciences Naturelles," Zool., Aout, 1846. 



5 "Ueber die Pacinischen Korperchen," Zurich, 1844. 



Terminal nerves, on the sac of the second 

 molar tooth of the lower jaw, in the sheep ; 

 showing the arrangement in loops. (After 

 Valentin.) 



6 "Cyclopaedia of Anatomy and Physiology," Art. " 

 jwman's "Physiological Anatomy," p. 345, Am. Ed. 



Pacinian Bodies," and Todd and 



