CHAPTER XCTV 



EFFECTS OF EXPERIMENTAL LESIONS OF VARIOUS PARTS 



OF THE NERVOUS SYSTEM 



Saving Learned the main characteristics of reflex action, we shall now 

 proceed to study the peculiar function of each part of the cerebrospinal 

 system by noting tin- effects which follow destruction or stimulation of 

 its different parts. 



THE ANTERIOR ROOT 



Section of an anterior root produces a limited degree <>f paralysis in- 

 volving several muscles having no functional relationships to one an 



other. If several anterior roots are cut, the paralysis b mes much 



more extended, and is followed yery soon by an evident atrophy of the 

 muscles concerned. Reflex actions from these muscles are of course im- 

 possible, stimulation of the peripheral end of a cut motor root cai 

 partial contraction of several muscles, no definite joint movement, how- 

 ever, being the result, because the affected muscles are not functionally re- 

 lated and there is no reciprocal inhibition Flexor and extensor, adductor 

 and abductor may contract at the same time, thus causing the joint on which 

 they act to become muscle-bound. It is in the plexus that the nerve 

 fibers of the roots become suited out, according to function, into motor 

 and sensory nerve trunks. The distribution of the anterior root fibers 

 according to segments in man for the cervical and lumbosacral regions 

 is as follov 8: 



id, biceps, brachialis, supinators, rhomboids. ally 



radial extensors. Rarely pronator radii 

 C6 Pronators, radial extensors, peetoralia major (clavicular fibers 



Berratns antiens. 

 C7 Triceps, extensor carpi ulnaria • - lingers, peetoralia 



major. 

 OS Pl( icora of "i i-' and I 

 Tl Intrinsic muscles of hand. 



• ; ti.i ani, sphincter ani, perineal muscli 

 Glutei, biceps, Bemitendinosus and semimembranoa 



SI Intrinsic muscles of foot, tibialis ; 9, ami : 



LS Muscles of ventrolateral leg t tibialis anticu 



l.t Extensor! g and tibialis anti. 



