416 SPECIAL HISTOLOGY. 



§ 122. Cerebral Nerves. — The sensitive and motor nerves arising in 

 the brain, correspond in most particulars so closely with the spinal 

 nerves, that a short description of them will suffice ; and with respect 

 to the higher nerves of sense, they Avill be afterwards described, more 

 fully, in connection with the organs to which they belong. 



The motor cerebral nerves, the third, fourth, sixth, seventh, and 

 twelfth pairs, with respect both to their roots and to their course and 

 distribution, present exactly the same conditions as the motor roots and 

 muscular branches of the spinal nerves, with the sole exception, that by 

 all these nerves, from their anastomosing with sensitive nerves, some 

 sensitive fibres are conveyed to the muscles. It deserves remark : 1, 

 that according to Rosenthal and Purkinje, nerve-cells exist in the trunk 

 of the oculo-motorius in the Ox, which, however. Bidder (p. 32) was 

 unable to find ; 2, that the facial nerve, in its gangliform enlargement, 

 presents a number of larger nerve-cells, through which, however, accord- 

 ing to Reraak, only part of the fibres pass (Miill. " Archiv." 1841); 

 3, that according to Volkmann (in Bidder's " Ganglien-kcirper," p. 68), 

 the small root of the hypoglossal nerve in the Calf, which is furnished 

 with a ganglion, produces motor effects. What is the significance of 

 this occurrence of nerve-cells in motor nerves has not been ascertained. 

 Probably simple fibres having a peripheral destination arise from them, 

 exactly as in the spinal ganglia. In any case it shows that ganglia are 

 not necessarily placed only on sensitive nerves. The fifth, ninth, and 

 tenth pairs, resemble the spinal nerves, inasmuch as that they all con- 

 tain motor and sensitive elements. In the trigeminus the small root 

 exhibits a preponderance of thick fibres; the larger, numerous fine 

 fibres. The Gasserian ganglion, as well as the smaller ganglionic body 

 seated upon it, contains many larger and smaller nerve-cells of O'OOS- 

 0-030 of a line, with nucleated sheaths, and presents the same conditions, 

 according to my observations, in small Mammalia and in Man, as a spi- 

 nal ganglion, that is to say, it is simply traversed by the fibres of the 

 greater root, and, from unipolar cells, gives origin to numerous nerve- 

 fibres of medium size, which go to join the emergent branches. Bipolar 

 cells also occur, but, as it appears, in less quantity, and anything that 

 can be said about apolar cells is as applicable here as in the case of the 

 spinal ganglia. The ultimate distribution of the n. trigeminus is for the 

 most part similar to that of the cutaneous nerves, and, in particular, the 

 existence of divisions of the nerve-tubes may be distinctly demonstrated 

 in the mucous membranes, as in the conjunctiva at the edge of the cor- 

 nea, in the ciliary ligament, in the tooth-pulp, and in the papillae of the 

 tongue. Terminal loops and free terminations appear to exist in the 

 papillffi of the mucous membrane of the mouth and tongue, and in the 

 conjunctiva, whilst in the cornea, the extremities of the nerves are quite 



