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



the flexores breves wandering to the dorsum of the foot and acting as extensors ; and 

 in some marsupial and monotrematous animals a new and opposite action added to the 

 abductors, viz., that of approximation. 



Fig. 3. Schematic view of a transverse section through the metatarsus of a typical foot. 

 (jt) 1 to y 5 ) Adductores. (/' to/ 5 ) Flexores breves. (d l to d s ) Abduetores. (e.p.n.) External plantar nerve. 



The flexor brevis indicis is completely lost in the human foot — not a trace of it is to 

 be found. 



General Remarks. 



Plantar layer. — To Bischoff and Halford is due the credit of being the first to 

 describe an adducting muscular apparatus homologically distinct from the other intrinsic 

 muscles of the hand and foot. Bischoff's observations were confined to the Apes, and 

 he did not include as a part of this apparatus the adductor hallucis. It is true that 

 many writers had previously noted the presence of adducting muscles, but all had 

 failed to recognise their true import. Professor Halford not only gives an account 

 of the muscles composing this layer in the foot of the Macacus, but he applies 

 to them the distinctive name of " contrahentes digitorum " — a name which Bischoff 

 adopts. In the abstract of this portion of my report which I published in the 

 Journal of Anatomy and Physiology in 1878, I described these muscles in a large 

 number of the lower mammals, and placed the adductor hallucis amongst them. To the 

 group thus constituted I gave the name of "plantar layer of adductors." In this paper, 

 however, I fell into the error of considering the plantar interossei of the human foot as 

 members of the layer. A few months later, Ruge's article upon the Deep Muscles of the 

 Sole of the Foot appeared, in which he also recognised the true position of the adductor 

 hallucis by placing it amongst the contrahentes or adductors. Further, he pointed out, 

 by means of the deep division of the external plantar nerve, that the adductores digitorum 



