THE DISCOVERY OP MOTOR AND SENSORY NERVE CHANNELS. 289 



The best passages that can be quoted on the side of Bell from the 

 ' Idea ' of 18 J J are as follows: — 



Page 21. — I took this view of the subject. The medulla spinalis has a cen- 

 tral division, and also a distinction into anterior and posterior fasciculi, cor- 

 responding with the anterior and posterior portions of the brain. Further, we 

 can traoe down the crura of the cerebrum into the anterior fasciculus of the spinal 

 marrow, and the crura of the cerebellum into the posterior fasciculus. I thought 

 that here I might have an opportunity of touching the cerebellum, as it were, 

 through the posterior portion of the spinal marrow, and the cerebrum by the 

 anterior portion. To this end I made experiments which, though they were not 

 conclusive, encouraged me in the view I had taken. 



I found that injury done to the anterior portion of the spinal marrow con- 

 vulsed the animal more certainly than injury done to the posterior portion ; 

 but I found it difficult to make the experiment without injuring both portions. 



Next considering that the spinal nerves have a double root, and beins of 

 opinion that the properties of the nerves are derived from their connections 

 with the parts of the brain, I thought that I had an opportunity of putting my 

 opinion to the test of experiment, and of proving at the same time that nerves of 

 different endowments were in the same cord, and held together by the same 

 sheath. 



On laying bare the roots of the spinal nerves, I found that I could cut across 

 the posterior fasciculus of nerves, which took its origin from the posterior 

 portion of the spinal marrow without convulsing the muscles of the back; but 

 that on touching the anterior fasciculus with the point of the knife, the muscles 

 of the back were immediately convulsed. 



Such were my reasons for concluding that the cerebrum and the cerebellum 

 were parts distinct in function, and that every nerve possessing a double func- 

 tion obtained that by having a double root. I now saw the meaning of the 

 double connection of the nerves with the spinal marrow ; and also the cause of 

 that seeming intricacy in the connections of nerves throughout their course, 

 which were not double at their origins. 



The spinal nerves being double, and having their roots in the spinal marrow, 

 of which a portion comes from the cerebrum and a portion from the cerebellum, 

 they convey the attributes of both grand divisions of the brain to every part ; 

 and therefore the distribution of such nerves is simple, one nerve supplying 

 its destined part. But the nerves which come directly from the brain come 

 from parts of the brain which vary in operation; and in order to bestow 

 different qualities on the parts to which the nerves are distributed, two or more 

 nerves must be united in their course or at their final destination. Hence it is 

 that the 1st nerve must have branches of the 5th united with it: hence the 

 portio dura of the 7th pervades everywhere the bones of the cranium to unite 

 with the extended branches of the 5th : hence the union of the 3rd and 5th in 

 the orbit : hence the 9th and 5th are both sent to the tongue : hence it is, in 

 short, that no part is sufficiently supplied by one single nerve, unless that nerve 

 be a nerve of the spinal marrow, and have a double root, a connection (however 

 remotely) with both the cerebrum and cerebellum. 



Page 26.— The cerebellum when compared with the cerebrum is simple in its 

 form. It has no internal tubercles or masses of cineritious cortex, and forms 

 the c rus ; and the cms runs into union with the same process from the cerebrum ; 

 and they together form the medulla spinalis, and are continued down into the 

 spinal marrow; and these crura or processes afford double origin to the double 

 nerves of the spine. The nerves proceeding from the Crus Cerebelli go every- 

 where (in seeming union with those from the Crus Cerebri) ; they unite the body 

 together, and control the actions of the bodily frame; and especially govern 

 the operation of the viscera necessary to the continuance of life. 



Page 27.— The cerebrum I consider as the grand organ by which the mind is 

 united to the body. Into it all the nerves from the external organs of the 

 senses enter; and from it all the nerves which are the agents of the will pass out. 



Page 36.— The secret operations of the bodily frame, and the connections 

 which unite the parts of the body into a system, are through the cerebellum and 

 nerves proceeding from it. 



1911. u 



