FUNCTIONS OF NERVES. 4-19 



acutely sensible : the division of the former portion has the same 

 effect as the division of the anterior nerves ; of the latter, as the 

 division of the posterior nerves. The destruction of the centre 

 of the spinal chord by a wire impairs neither sensation nor 

 motion k , nor is pain felt by the experiment: and I may remark 

 that, in experiments on the healthy cerebrum and cerebellum, no 



the matter confused and anomalous, by assuming the general belief of a branch 

 of this nerve of common sensation or touch serving for a special sense, for 

 taste. The perfect analogy of the trigeminum to the spinal nerves in having 

 one of its two divisions for common sensation only and one for motion is now 

 established by Professor Panizza, through his demonstration of the glosso-pharyn- 

 geal being the nerve of the special sense of taste, while the branches of the tri- 

 geminum going to the tongue are for its ordinary sensibility, just as those which 

 go to the mucous membrane of the nose endow it with the same common sensi- 

 bility, while the olfactory endow it with its special sense of smell. (See infra, 

 Chapter XXI. ON TASTE.) 



Dr. Magendie, finding that the division of the trigeminum deprived the nose, 

 eyes, &c. of the sense of touch, so that acrid substances no longer irritated, con- 

 cluded that it gave smell, sight, and taste, and threatened to overthrow the doctrine 

 of the optic nerve being for sight, the olfactory for smell, and so on. He mis- 

 took the loss of common feeling for the loss of the specific sensibility of the 

 eye, nose, &c., and his conclusions have long fallen to the ground. 



The opinion that there are distinct nerves for sensation and for motion had 

 been entertained ever since the time of Erasistratus by many writers, from the fact 

 of paralytic limbs being sometimes deprived of sensation only, sometimes of 

 motion only, or even, in the latter case, becoming more sensible than previously. 

 In Pouteau's (Euvres Posthumes, published in 1783, vol. ii. p. 532., it was main- 

 tained, but the author remarked that it had long been abandoned by anatomists. 

 He erred in supposing that the nerves of sensation came from the cerebrum, and 

 those of volition from the cerebellum : as Galen erred in saying that the nerves 

 of sensation arose from the brain, and those of voluntary motion from the spinal 

 chord. Certain nerves were known to be for sensation only, as the olfactory, 

 optic, and acoustic ; some for motion only, as the common motor of the eye, the 

 external and internal motor. Sommerring had pointed out that one nerve gave 

 motion to the tongue, another sensation : whence a man might lose his taste 

 and yet move his tongue as before (Him und Nerven, p. 255.) ; and Gall, in 

 1810, urged that his adversaries would find it difficult to prove that the same 

 nervous filament possessed the power of both feeling and motion ; and that 

 the trigeminum pair, which supplies both sense and motion, has three distinct 

 roots. (Anatomie et Physiologic, t. i. p. 129. sqq.) The morbid sensibility to warmth 

 occasionally observed in paralysis, although the sense of touch be not morbidly 

 acute or be actually impaired, induced Dr. Darwin to fancy there were distinct 

 nerves even for the sensation of temperature. (Zoonomia, Sect. xiv. 6.) 



k Dr, Magendie, Journal de Physiol. t. iii. p. 153. sq. 



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