204 THE VOYAGE OF H.M.S. CHALLENGER. 



tendon. All the slits of the other superficial tendons are lateral, and not antero-posterior as in the 

 other Seals. 



In Arctocephalus gazclla the insertion of the combined flexor tendons out of the union of the 

 flexor longus digitorum and the flexor longus hallucis forms a rectangular band, which divides at 

 the base of the 2nd metatarsal bone into two broad tendons, the ventral and the dorsal portions. 

 The ventral portion also divides into two, forming the flexor longus hallucis tendon and the first 

 or inner flexor longus digitorum tendon. The ventral or flexor longus hallucis slip runs backwards 

 to the terminal phalanx of the hallux, and after expanding is inserted chiefly into its proximal 

 plantar surface, and into the whole of the plantar surface of this phalanx, by the prolongation of 

 the tendon of insertion over the surface of the terminal bone. The first or inner flexor longus 

 digitorum tendon, formed out of the dorsal part of the ventral division of the main tendon, is 

 described with the following deep tendons. The outer or dorsal main portion breaks into three 

 slips, that for the 5th digit coining off higher than the other two. The four long flexor tendons thus 

 formed go backwards along the plantar sides of the 2nd, 3rd, 4th, and 5th digits to the distal 

 phalanges ; opposite the bases of the 1st phalanges they pass through the aponeurotic tunnels in 

 the short flexors formed from the plantaris, becoming anterior to them, and are inserted into the 

 phalanges as the tendon of the flexor longus hallucis. 



The action of these combined muscles in the Phocina? and Macrorhinus is to bring the pes 

 to the middle line and to bend the digits. In Arctocepludus they will raise the heel in walking, 

 otherwise they are the same. 



There is an important difference in the relation of the flexor longus digitorum and flexor 

 longus hallucis in the Phocinffi, Macrorlvinns, and Arctocephalus. In the first two the flexor 

 longus hallucis is to the dorsal side of the flexor longus digitorum from origin to insertion, but in 

 the last the flexor longus hallucis is superficial to the flexor longus digitorum and crosses anterior 

 to the ankle to the ventral side of the pes; and the flexor longus digitorum in the pes lies dorsal 

 to it — the reverse of what is found in the Phocinas and Macrorhinus. 



While recognising the intermingling of the tendons of the flexors, I find it impossible to work 

 out how far the tendons of the flexor hallucis and flexor longus digitorum cross each other to assist 

 in forming the flexors of the digits, and therefore I have described only what is easily made out. 



Humphry writes " in the case of the pollex the superficial tendon did not divide as in the 

 other toes." In my dissections of the Phocinas I find that the slip out of the combined tendon 

 comes off singly, and very soon divides into two long slips, one being the flexor longus hallucis and 

 the other the flexor brevis hallucis. The same author also explains that " the tendons of each muscle 

 (flexor longus hallucis and flexor longus digitorum) contributed some fibres to each of the tendons 

 (with the exception presently to be mentioned), but the deep tendons were derived mainly from 

 the flexor longus pollicis, the flexor digitorum being distributed chiefly to the superficial tendons. 

 The superficial tendon of the 4th digit was in one foot, and that of the 5th hi both, derived from 

 the plantaris." The flexor longus digitorum in the Phocinse is not crossed by the flexor longus hallucis 

 as in human anatomy, but they pass each other along their contiguous edges without crossing. The 

 two tendons for the most part keep their own side in the pes. The flexor longus digitorum gives 

 off the tendons for the hallux and 1st digit, the flexor longus hallucis for the 3rd, 4th, and 5th 

 digits. I find that the plantaris forms the anterior slip for the sheath of the 4th digit and not 

 the superficial tendon, and in the 5th digit the tendons were principally formed by the flexor 



