7-4 THE VOYAGE OF H.M.S. CHALLENGER. 



provided with rudiments of the three typical muscles which properly belong to this toe. 

 The index also has its complement of muscles, but these are not so distinctly mapped off 

 from each other, as in the case of the hallux. The minimus has an adductor and a flexor 

 brevis, whilst the annularis and medius are only furnished with adductors. But what is 

 particularly noticeable about these muscles is, that they are all (with the exception of 

 the flexor brevis minimi digiti) manifestly undergoing retrograde change. The adductors 

 indeed are so thin that they are semi-transparent. 



In the specimen which I dissected, the flexor longus digitorum sent no tendon to the 

 minimus, consecpiently the outermost belly of the flexor brevis digitorum (f.d) is retained 

 for this digit, and is very apt to be mistaken for an intrinsic muscle seeing that the other 

 three bellies are altogether suppressed. This solitary portion of the short flexor of the 

 toes takes origin from the plantar fascia and the tuber of the os calcis, and is inserted 

 into the plantar surface of the base of the second phalanx of the little toe. It is partially 

 fused with the subjacent flexor brevis minimi digiti which obscures its identity still 

 further. St. George Mivart, however, 1 in his well known memoir upon the Echidna 

 lujstrix, describes a tendon as passing from the long flexor of the toes to the minimus, 

 and denies the presence of any portion of the short flexor. 



Adductor or plantar layer (p 1 to £> 5 ). — This layer is well represented, each digit 

 being supplied with one, and the annularis with two. They are inserted so as to draw 

 the digits towards the interval between the index and hallux. 



The adductor hallucis (jj 1 ) and adductor indicis (p 2 ) arise by a common origin from 

 the under surface of the os calcis close to the outer margin of the foot. They cross 

 the sole oblicmely, and are placed superficial to the common origin of the other 

 members of this group. The adductor hallucis is a very slender sUp which, ending in 

 a minute tendon, is inserted into the outer side of the base of the ungual phalanx 

 of the hallux. The adductor indicis, more strongly marked, ends in a flat aponeu- 

 rotic tendon which is inserted upon the inner aspect of the second phalanx of the 

 index. 



The remaining adductors (p 3 , j^, and p h ) have a common origin from the ligamentous 

 textures upon the under surface of the tarsus, and diverge from each other to reach their 

 respective points of insertion. They are thin bands which end in flat aponeurotic 

 tendons. These are inserted into the tibial sides of the ungual phalanges of the medius. 

 annularis, and minimus respectively. The annularis possesses, however, a very delicate 

 additional fasiculus (p. 4 1 ) which seems to belong to this layer seeing that it lies superficial 

 to the deep division of the external plantar nerve, and arises in common with the three 

 outer members of the group. This minute slip is inserted into the plantar aspect of the 

 first phalanx of the annular digit. In all probability it is analogous to the additional 



1 Some Points on the Anatomy of Echidna hystrix, by St. George Mivart, F.L.S. (Trans. Linn. Soc, vol. .\xv. 

 p. 394). 



