1881.] 



The Brachial and Lumbo- Sacral Plexuses. 



13 



("Richerche Sperimentali Sopra i Nervi," Lettera del Professore 

 Bartolorneo Panizza al Professore Mauri zio Bufalini. " Annali 

 Universali di Medicina," December, 1834. Translated in " Froriep's 

 Notizen," No. 945, March, 1835.) 



Panizza found that section of one root caused only temporary 

 weakness of the limb as a whole, a weakness which increased in pro- 

 portion to the number of roots divided ; but there was no complete 

 paralysis till the last root was cut. He was of opinion that the 

 various roots had a community of function, the whole forming a 

 solidarity, but each by itself capable of maintaining the functions in 

 their integrity. 



The researches of Peyer (" Zeitschrift fur Rationelle Medicin," 

 N. F., Bd. iv, 1854) on the peripheric distribution of the sensory 

 and motor roots of the brachial plexus in the rabbit were of greater 

 precision than those of Kronenberg. 



Peyer cut the roots of the plexus and ascertained, by exposure and 

 dissection, which muscles were made to contract by weak electrical 

 stimulation of each root. He also determined the region of distribu- 

 tion of the sensory roots by cutting all the roots save one, and then 

 ascertaining in which area cutaneous stimulation still excited reflex 

 movements. 



The results obtained by Peyer as to the distribution of the motor 

 roots differ considerably from those of Kronenberg, and he gives, in a 

 tabular form, the respective muscles related to each root, from the 

 fifth cervical to the first dorsal. 



He found that most muscles received fibres from more than one 

 root, and that the muscles supplied by each root did not fall into such 

 simple groups as extensors, flexors, (tec, but were more complicated. 

 The muscles nearer the hand were supplied by the roots nearer the 

 dorsal part of the cord. As regards the sensory distribution, the rule 

 was that the sensory roots were distributed to the cutaneous surfaces 

 overlying the muscles supplied by the corresponding motor roots. 



Peyer's results were, in the main, confirmed by the researches of 

 W. Krause ("Beitrage zur Neurologie der Oberen Extremitat," 1865). 

 Krause adopted the method of dividing the individual roots and then 

 tracing the lines of degeneration in the sensory and motor nerves, 

 according to the Wallerian law. He gives a tabular view of the 

 peripheric distribution of the various roots, sensory and motor, in 

 the work quoted, and again, with slight variations, in his work on the 

 anatomy of the rabbit (" Anatomie des Kaninchens," 1868, p. 247). 



Krause also made one interesting experiment on a monkey (Macacus 

 cynomolgus) . He divided the sixth and seventh cervical nerves, and 

 ascertained that no degeneration ensued in the ulnar or median 

 sensory nerves of the hand. He concluded, by analogy from "the 

 ascertained distribution in the rabbit, that the ulnar and median 



