HUMPBACK \YHALE. 295 



These percentages show a general agreement, but indicate a relatively smaller head in 

 proportion to total length in the smaller animal. The only other striking difference is in the 

 relative breadth of the flukes, which is much less in the latter. 



Musculature. 



Forearm and Finger Muscles. — Notwithstanding the great size of the pectoral lim])s in 

 the Humpback, the muscles of the forearm and fingers are actually "not half the size" of the 

 same muscles in the Finback, as Struthers has shown. He found four of these muscles devel- 

 oped, the same four that are present in the Finback. He describes the flexor carpi ulnaris as 

 thick and fusiform, not spreading fan-like as in the Finback although it is not of less size. Its 

 origin is entirely on the cartilaginous olecranon, or ell)ow, and it is fleshy for about half its 

 length or 11 inches, after which it passes into a tendon of elliptical cross-section, and inserts 

 into the proximal border of the pisiform cartilage. 



The flexor digitcrrum ulnaris resembles the same muscle in the Finback but is much smaller. 

 It is a flattened narrow muscle, about 1.5 inches in greatest width at the middle. Its origin 

 is from the ulna and its long tendon joins that of the flexor digitorum radialis. The latter is 

 the larger, and arises from the ulna as well as from the radius. At about the junction of the 

 middle and distal thirds of the forearm its tendon joins that of the flexor d. ulnaris, and a tendi- 

 nous expansion is here formed, from which a separate tendon runs to the end of each digit. 



On the upper side of the flipper is but a single well developed muscle, the extensor digitorum 

 communis. Like the others, this is fleshy for but a short distance from its origin at the proxi- 

 mal portion of both radius and ulna. It soon narrows to a large tendon which forms a triangu- 

 lar expansion on the distal half of the carpus. From this pass off the four tendons, one to each 

 digit. That to digit II is the largest, that to digit V the smallest. These tendons are attached 

 to all the joints of the phalanges, and serve apparently through their tension to give additional 

 stiffness to the great paddles. 



Pelvic Muscles. — Struthers has given an account of the muscles attached to the ves- 

 tigial pelvic bones and femora. The relations are in general similar to those in the Fin- 

 back. "Passing across between the posterior ends of the pelvic bones is the great interpelvic 

 ligament. . . .It ties the pelvic bones together posteriorly, and supports the crura penis, which 

 are involved in its tissue anteriorly, and entirely rest on it. Behind, it attaches the anterior 

 part of the levator ani muscle, and more externally the inner part of the caudal muscular mass. 

 Along the posterior edge of the great ligament is seen the posterior edge of the transversus perinei 

 muscle mostly concealed by and attached to the ligament; as broad and as thick as the palm 

 of the hand and 6 to 8 inches in length transversely. In the ring between this muscle and 

 the beginning of the levator ani muscle, is seen the retractor penis muscle, rope-like, right and 



