THE BEACRIAL PLEXUS. 



767 



Fig. 352. 



the Dog furnishes branches to all the digits, except the auricularis and external border 

 of the annularis. 



In the Cat, the median traverses the bony canal at the lower extremity of the 

 humerus, and separates below the carpal arch into three branches. The internal 

 branch is destined to the rudimentary thumb, and the internal palmar border of 

 the index. The middle branch descends in the third iuterosseous space, furnishes a 

 filament to the large cushion of the paw, 

 and divides to form the external palmar 

 collaterals of the index and internal of the 

 medius. Finally, the external branch is 

 placed in the second intermetacarpal space, 

 and gives the following palmar collaterals : 

 the external of the medius and internal of 

 the annularis. 



The ulnar nerve of the Dog, below the 

 elbow, lies beside the ulnar artery to the 

 lower third of that vessel ; there it forms 

 two branches a dorsal and palmar. The 

 dorsal branch becomes subcutaneous, passes 

 along the external border of the fore-arm, 

 metacarpus, and small digit, and con- 

 stitutes the external dorsal collateral nerve 

 of the latter. 



The palmar branch leaves the carpal 

 sheath, gives off, at the trapezoides, a ramus- 

 cule that passes to the surface of the palmar 

 muscles to form the external collateral pal- 

 mar of the auricularis, and then, at the 

 surface of the deep palmar arch, divides into 

 eight terminal ramuscules. The smallest 

 of these is expended in the rudimentary 

 muscles of the thumb, the small digit, and 

 interosseous muscles; the largest, three in 

 number, lie on the interosseous arteries, and 

 bifurcate at the digits to form the palmar 

 collaterals ; the two internal ramuscules are 

 previously confounded with the correspond- 

 ing branches of the median. From this 

 arrangement, it results that the ulnar nerve 

 supplies the palmar surface of all the digits, 

 except the internal border of the index. 



The ulnar of the Cat also divides into 

 a dorsal and a palmar branch, but the dis- 

 tribution of these is not the same as in the 

 Dog. 



The dorsal branch bifurcates at the car- 

 pus : one of the filaments forms the external 



dorsal collateral of the small digit; the 

 other reaches the first interosseous space, 

 receives a branch from the radial, and after- 

 wards gives off the internal dorsal collateral 

 of the small digit, and external of the 

 auricularis. 



The palmar branch does not extend to 

 all the digits as in the Dog. Passing within 



the pisiform bone, it divides into several filaments : some of these are distributed to the 

 muscles of the small digit and thumb ; another follows the external border of the bmall 

 digit, and constitutes its external palmar collateral ; one of the longest is lodged in the 

 first intermetacarpal space, giving a filament to the large cushion of the paw, and 

 the internal palmar collaterals of the small digit and external of the annularis. 



NERVES OF THE PALMAR FACE; CAT. 



A, Trunk of the median dividing into two 

 branches ; B, Internal branch, giving a 

 rudimentary filament to the thumb; Bl, 

 External branch, receiving a filament, /, 

 from the ulnar ; c, C, C, C, Collaterals fur- 

 nished by the median. a, Palmar branch 

 of the ulnar dividing into three branches ; 

 6, Internal branch, detaching the filament, 

 /, to the median ; 61, External branch ; 62, 

 Deep branch ; c, c, c, Collaterals furnished 

 by the ulnar. 



COMPARISON OF THE BRACHIAL PLEXUS OF MAN WITH THAT OF ANIMALS. 



The brachial plexus of Man, like that of the Dog, is constituted by the anterior 

 branches of the four last cervical, and the last dorsal nerves. The few variations observed 



