The Minute Anatomy of the Brachial Plexus. 437 



tract together, are supplied by the same nerve ? The action of the 

 two pronators is indistinguishable, but the teres is supplied by the 

 6th, and the quadratus by the 8th and 9th ; the thumb is always acting 

 with the fingers, yet the superficial thenar muscles are served by tbe 

 6th, and the others by the 8th. 



It seems then certain that the place where functions are represented 

 is higher than the peripheral nerves, and that these are distributed 

 according to some other plan. 



The other system that suggests itself is the system according to 

 place, and I find that the nerve supply of the muscles of the upper 

 limb obeys three rules. 



LAW II. — A. Of two muscles, or of two parts of a muscle, that 

 which is nearer the head-end of the body tends to be supplied by 

 the higher, that which is nearer the tail-end by the lower 

 nerve. 



B. Of two muscles, that which is nearer the long axis of the body tends 



to be supplied by the higher, that which is nearer the periphery by 

 the lower nerve. 



C. Of two muscles, that which is nearer the surface tends to be supplied 



by the higher, that which is further from it by the lower nerve. 



The first rule has been already clearly exemplified in the supply of 

 large flat muscles which receive more than one nerve, such as the 

 pectoralis major and serratus magnus. The subscapularis is also an 

 example. In all these muscles it was shown that the upper parts 

 were supplied by upper, the lower by relatively lower nerves. It 

 remains to show how it is exemplified in the remainder of the muscles 

 belonging to the limb. 



It has been laid down that in the first position of the foetus the 

 great tuberosity and the external condyle of the humerus, the radius 

 and the thumb are turned towards the head ; the lesser tuberosity, 

 the internal condyle, the ulna, and the little finger towards the tail. 

 The first set of points have been called pre-axial, the latter post-axial. 

 The muscles corresponding with the pre-axial points will be found to 

 be supplied by higher nerves than those connected with post-axial 

 points at the same level of the limb. 



Of the muscles which connect the scapula to the spine, the highest 

 is the levator anguli scapulas. This is supplied by the 3rd and 4th, 

 and slightly by the 5th. Below this come the rhomboids supplied by 

 the 5th alone. Of the muscles which join the humerus to the scapula 

 those inserted into the outer or pre-axial tuberosity are supplied by the 

 5th, with very slight, if any, aid from the 6th. Of those going to the 

 post-axial part, the subscapularis, which is the highest, is supplied by 

 the 5th and 6th ; the teres major below it is supplied by the 6th, the 

 latissimus dorsi which comes from lower down the body, and the 



