12 



Profs. D. Ferrier and G. F. Yeo. 



[Mar. 24, 



II. " The Functional Relations of the Motor Roots of the Brachial 

 and Lumbosacral Plexuses." By David Ferrier, M.D., 

 F.R.S., Professor of Forensic Medicine, and Gerald F. 

 Yeo, M.D.. F.R.C.S., Professor of Physiology in King's 

 College. Received March 10, 1881. 



The functions subserved by the plexiform arrangement of the 

 nerves of the limbs, and the mode of distribution of the several roots 

 of the brachial and lumbo-sacral plexuses, have been the subject of 

 frequent speculation and of occasional experimental research ; and 

 the question is one of considerable physiological and pathological 

 interest. A mere naked-eye examination of the mode in which the 

 roots unite to form the larger trunks allows of an approximate deter- 

 mination of the possible roots of each trunk ; and by more minute 

 dissection and maceration in dissociating liquids, as has been done by 

 W. Krause in the case of the brachial plexus ("Beitrage zur 

 Neurologic der Oberen Extremitat," 1865), the constituent fibres of 

 the nerve-trunks may be determined with greater precision. 



But it is obvious that anatomical dissection, however minute, is 

 unable to discriminate between the sensory and motor constituents of 

 the nerve-trunks, or to indicate their functional relations and dis- 

 tribution. The only possible methods by which this can be arrived at 

 are by determining the effects of excitation or destruction of the 

 individual roots of the plexus. 



Both methods have been employed by different investigators in the 

 case of several of the lower animals. 



Johannes Miiller and Van Deen experimented on the crural plexus 

 of the frog. From these, as well as from a consideration of the 

 results of Kronenberg's experiments referred to below, Miiller came 

 to the conclusion that " the plexuses of nerves seem to be destined, 

 as far as their motor power is concerned, to convey to each muscle 

 fibres from different parts of the brain and spinal cord. . . . The 

 plexuses may also be intended to intermingle the sensitive and motor 

 fibres in accordance with the wants of the parts to which the nerves 

 are distributed " (Miiller' s " Physiology," translated by Baly, vol. i, 

 p. 682), Kronenberg (" Plexuum Nervorum Structura et Virtutes," 

 Berol, 1836, quoted by W. Krause, op. cit.) found that by mechanical 

 or electrical stimulation of the roots of the brachial plexus in the 

 rabbit, almost every muscle of the limb was thrown into action by 

 each. His conclusions as to the functions of the plexus were essentially 

 the same as those quoted from Miiller. 



A similar view was maintained by Bartolomeo Panizza, from the 

 results of experiment on the crural plexus of frogs and goats. 



