SECT. 120.] NERVOUS SYSTEM. 247 



It cannot be ascertained anatomically where the ganglionic fibres, 

 which arise in the spinal ganglia, are distributed. When their 

 physiological relations, however, are considered, it seems most 

 probable that they do not, or at least not all, as one might at first 

 be inclined to believe, join the sympathetic in the rami communi- 

 cantes, but running along with the spinal nerves, pass especially into 

 the vascular branches, and are, consequently, distributed in the skin, 

 muscles, bones, joints, tendons, and membranes (periosteum, pia 

 mate?', etc.), and perhaps, also, in the glands and involuntary 

 muscular tissue of the skin. The nerve-fibres in the main divisions 

 of the spinal nerves present the same diameter as in the roots, i.e., 

 there are finer and thicker tubes, and a certain number of transi- 

 tional forms. Further on, however, the fibres separate, the thicker 

 passing more into the muscular branches, and the thinner into the 

 cutaneous nerves. According to the statements of Bidder and 

 Volkmann, the relation, in man, of the thin to the thick fibres in 

 the nerves of the skin is as i*i : 1 ; in the muscular nerves, as o'i 

 — 0*33: 1. I can only confirm these statements, and may add 

 that the nerves of the bones contain one-third thick, two-thirds 

 thin tubes in the trunks, whilst those of the joints, tendons, and 

 membranes contain chiefly thin fibres. 



The spinal nerves consist, in general, of parallel tubes, mostly 

 with au undulating course, to which circumstance, also, their trans- 

 versely banded appearance is due ; but present, however, in their 

 course very frequent conjunctions, by which the different larger 

 and smaller plexuses, with their decussating fibres, are produced. 

 These plexuses are formed by an exchange of whole bundles of 

 fibres, never by a coalescence of the individual primitive fibres, 

 and present, in a microscopical point of view, nothing worthy of 

 note. As far as is hitherto known, divisions of the nerve-tubes do 

 not occur in the trunks and larger branches of the spinal nerves 

 of mammalia, and, in like manner, there is not any considerable 

 change in their diameter; but, on the other hand, even in man, 

 such divisions, and, at the same time, a very considerable decrease 

 of the diameters of the tubes, takes place in the terminal rami- 

 fications. With reference to these particulars and the nerve-ter- 

 minations in the skin, muscles, bones, and membranes in general, 

 we refer the reader to the more detailed description given in the 

 paragraphs treating of the parts in question. 



One mode of termination of the spinal nerves has here still to 

 be mentioned, that in the Pacinian bodies. These bodies, called 

 so by Henle and me (Ueber die Pacin. Korperchen d. Menschen und 



