26 PROCEEDINGS OP THE NATIONAL MUSEUM vol.80 



Anastomosis of the median and musculocutaneous nerves is not un- 

 common in man, but in such cases the branch is commonly from the 

 musculocutaneous distalward to the median (Spalteholz) and more 

 rarely vice versa, as we found in Ateles, Papio, Pygathrix, and 

 Lasiopyga. 



Bolk described anastomoses of the median and musculocutaneous 

 nerves in many of the primates that he dissected. In some instances 

 (as in Golobus ursinus, Macacus niger, Cynocephalus hahuin, O. 

 morTTion, and Mycetes seniculvs) the connecting branch passed from 

 median to musculocutaneous, as we found also in Ateles geofroyi 

 and Papio hannadryas; in one {Lepilemur viustelinus) it passed in 

 the opposite direction as is usual in man. In SeTnnopithecus nasicus 

 both median and musculocutaneous supplied a fine branch, which 

 joined together and innervated the coracobrachialis medius; while 

 in Cercopithecus alhigularis there was a twofold anastomosis of 

 median and musculocutaneous, the upper forming a purely motor 

 nerve to the brachialis muscle, the lower becoming the lateral 

 cutaneous nerve of the forearm. Anastomoses of musculocutaneous 

 and median have also been discussed by Kohlbriigge (1897) in some 

 detail. 



We found that all the brachial nerves of Hylohates lar were gath- 

 ered within a single sheath. This led to the first impression that 

 the musculocutaneous nerve was not present as a separate structure, 

 the nerves to the brachial flexors seeming to issue from the median. 

 Fortunately, however, our specimen was dissected while fresh, so 

 that upon splitting the common sheath the separate flexor nerves 

 could be readily demonstrated. In an embalmed specimen this 

 arrangement might easily have led to an erroneous interpretation. 

 Apparently the fibers of the musculocutaneous nerve in Hylo'bates 

 exhibit considerable variability in their degree of independence of 

 the median nerve. Kohlbriigge (1890), for example, found no sepa- 

 rate musculocutaneous nerve in either Hylo'bates syndactylus or H. 

 ngilis. In both of these animals the nerves to the three brachial 

 flexors arose as separate branches of the lateral head of the median 

 nerve. Bolk (1902), on the other hand, found in Eylohates 

 7)iulleri, a common trunk in the upper arm representing the united 

 musculocutaneous, median, and ulnar nerves. Only near the elbow 

 did this trunk divide into median and ulnar. Prior to this point 

 there were given off from the common trunk the separate branches 

 to the brachial flexors. In our Hylohates lar at least the association 

 of the flexor nerves in the brachium was not so intimate as that 

 described by Bolk, This author likewise found no separate musculo- 

 cutaneous nerve in his chimpanzee, the brachial flexors being served 



