The Minute Anatomy of the Brachial Plexus. 423 



" The Minute Anatomy of the Brachial Plexus." By W. P. 

 Herringham, M.B., M.R.C.P. Communicated by W. S. 

 Savory, F.R.S. Received March 8, — Read March 25, 

 1886. 



It has for some time appeared probable that the spinal nerves which 

 form the brachial plexus do not become confounded one with another, 

 but retain each its separate course and its separate functions. 



To the naked eye a nerve is a bundle of parallel threads bound 

 together, and at the same time divided by a sheath of connective 

 tissue. It seemed to me possible that the course of the spinal nerve 

 roots could be traced by a dissection which should follow each through 

 the plexus to the nerves which branch therefrom, and in these to its 

 final destination. 



My dissections were partly upon foetuses or stillborn children, partly 

 upon the adult. The plexus of an infant is in some respects better, 

 in some worse than that of an adult for an investigation of this kind. 

 On the one hand its minuteness needs the confirmation of larger 

 tissues, but on the other hand the fibrous sheath uniting the nerves is 

 very much weaker and less perfect, so that as in the case of the 

 pectorals, the serratus magnus, and coraco-brachialis muscles, arrange- 

 ments which in the adult need great care in dissection, can be seen in 

 the infant without using the knife at all. 



Adult bodies are best fitted for tracing fibres down a long nerve. 



The present paper is based upon the dissection of fifty-five plexuses, 

 thirty-two being foetal or infantile, and twenty-three adult. 



The 5 th cervical nerve as it lies between the scaleni gives off: a 

 branch which divides into the nerve to the rhomboids, and the upper 

 root* of the posterior thoracic. The latter is joined by the root from 

 the 6th, and lower down by one or sometimes two branches from 

 the 7th. 



In the adult the 5th and 6th usually join before the first digitations 

 of the serratus magnus are reached, and receive the 7th about the 

 level of the first rib. It can generally, even in adults, be seen that 

 the 7th joins the nerve below the twig given to the first part of the 

 muscle formed by the two upper digitations, and it is often easy to 

 separate the 5th from the 6th, and this from the 7th, so far as to show 

 that the first part of the muscle is supplied wholly by the 5th, and the 

 second by the 6th alone, or by the 5th and 6th, while the 7th does not 

 give twigs until the third part is reached. I have several times been 

 able to show this to students in the dissecting room. But in the 

 foetus there, is no dissection necessary. The branch to the first part 

 is given off before the 5th reaches the 6th, and the 7th does not enter 



