THE PELVIC LIMB 



in a satisfactory degree the lunate rear border theoretically desirable in 

 such a propulsive apparatus. 



Fortunately it is possible to present some myological evidence in this 

 discussion of the sea otter. There is available from the National Mu- 

 seum the skinned carcass of one of these animals that was brought from 

 Copper Island by Dr. Stejneger in 1897. This was evidently dried out 

 at least once, for the muscles are leathery and the nerves brittle. Never- 

 theless it is entirely suitable for investigating those muscles which 

 might be expected to shed some light on the method of swimming em- 

 ployed. Accordingly the more significant muscles of the hind limb are 

 described and figured (fig. 46). Nothing further is attempted for I 

 have no wish to encroach upon the chosen field of E. R. Hall in investi- 

 gating the comparative anatomy of the Mustelidae. 



Reference to the illustration shows that the muscle usually termed 

 caudofemoralis is large and powerful. It arises from the dorsal fascia, 

 superficial except caudally where origin is deep to the semitendinosus. 

 Insertion is upon the distal half of the femur and to the knee. At least 

 in the majority of cases this muscle is merely the chief part, usually the 

 whole, of the true gluteus maximus, for it is served, in the case of the 

 sea otter as in others, by the inferior gluteal nerve. And what is so 

 often called the gluteus maximus, where the term caudofemoralis is 

 also employed, is proven by the innervation to be the gluteus medius. 



The tensor fasciae latae arises by tough aponeurosis from the ilium, 

 and mediad from over the gluteus medius to an aponeurotic insertion 

 upon the femur for a considerabe distance distad of the greater tro- 

 chanter. It seemed to be innervated by a nerve thread coming from deep 

 between the main gluteal mass and the quadriceps. This was undoubtedly 

 a branch of the superior gluteal nerve, as usual, but was so brittle that 

 it broke and I was unable later to pick it up again. 



As is so often the case the main gluteal mass was separable only with 

 difficulty, the whole being fused toward insertion. It was so deep (23 

 mm.) and hardened that the only way the innervation could be deter- 

 mined was to pick the muscle to pieces, fiber by fiber. Three parts of 

 origin could be detected. Gluteus A arose thinly from the tip of the 

 ilium. The portion B arose from the dorsal fascia both craniad and 

 mediad of the ilium. Both A and B increased rapidly in thickness and 

 soon fused with the deeper and more robust part C, which arose from 

 the entire lateral aspect of the ilium, the whole inserting very strongly 

 upon the greater trochanter. The arrangement of the fibers was slightly 

 multipenniform and the mass constituted a muscle of great strength. 



[287} 



