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



Dorsal layer. — This layer like the preceding is not represented by its full complement 

 of muscles. It is composed of — (l) an abductor ossis metatarsi minimi digiti which 

 presents the usual attachments ; and (2) four dorsal interossei which are arranged so as to 

 abduct the digits, with reference to a line drawn through the medius. This digit there- 

 fore is provided with two members from this group. 



The absence of the abductor minimi digiti is readily accounted for by an examination 

 of the outer head of the flexor brevis of this toe. The great bulk of this slip, and the 

 fact that it takes its origin at a more proximal point than its neighbours (from the 

 surface of the long plantar ligament) leads to the conclusion that the lost muscle has 

 coalesced with it. Upon similar grounds also we conclude that the absent abductor 

 hallucis is contained within the inner head of the flexor brevis of the hallux. 



Dr. Euge in his article upon the deep muscles of the sole gives a figure of the 

 adducting muscles in the foot of the Meles vulgaris. These agree with the above 

 description, except in so far that they take origin on different planes. 



Lutra vulgaris (Otter), (PL VIII. fig. 2). 



Although the five digits of this foot are contained within a common web of integu- 

 ment, they nevertheless enjoy a wide range of movement, and in consequence the intrinsic 

 muscles are well developed. In their arrangement they show a certain similarity to 

 the same muscles in the Badger, but they approach much more closely the trilaminar dis- 

 position. Indeed, with one or two exceptions of minor importance, this foot may be 

 said to meet all the requirements of the typical arrangement. 



The plantar or adducting layer (p 1 , p 2 , p 6 ) corresponds in the number and character 

 of its elements with that of the Badger. As in the tetradactylous Carnivora, however, an 

 opponens minimi digiti (o.m) is developed in connection with the adductor of that toe. 

 This muscle is inserted into the plantar face of the distal third of the fifth metatarsal bone. 



The intermediate flexores breves (f 1 to/" 5 ) show only a very slight tendency to fusion 

 with the dorsal interossei. Each digit, with the exception of the hallux, is provided with 

 a double-headed muscle. The flexor brevis hallucis, however, is represented by a single 

 inner head. 



The dorsal muscles (d 2 to d 6 and a.o) are arranged in a manner similar to those in the 

 foot of the Badger, with the exception that we find a small abductor hallucis present, 

 — quite separate from the inner head of the flexor brevis of that digit. 



Mustela putorius (Pole-Cat). 



With regard to the pes of the Pole-Cat, my observations do not extend beyond the 

 adducting muscles. The animal was so putrid that a dissection of the deeper layers was 

 impossible. I made out with certainty, however, that the adductors were identical both 

 in point of number and mode of disposition with the corresponding muscles in the Otter 

 and the Badger. Further, like the former, it possesses an opponens minimi digiti 

 developed in the same way. 



