FUNCTIONS OF MOTOR AND SENSORY NERVES 83 



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 portion of the spinal 

 marrow without convulsing the muscles of the back ; but 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 function obtained that by 

 having a double root. I inow 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, 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 Jbranches of the 5th united with it: hence the porHo 

 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." 



P. 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 cms ; and the crus 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 cura or processes afford double origin to 

 the double nerves of the spine. The nerves proceeding from 

 the Crus Cerebelli go everywhere (in seeming union with those 

 from the Crus Cerebri) ; they unite the body together, and 

 control the actions of the bodily frame ; and especially 



