1894.] MAMMALIAN HAND AND FOOT. 373 



(" abductor prcehallucis"), but I am inclined to take this muscle 

 together with the gastrocnemius (and soleus when present) as the 

 superficial flexor digit, longus. I do not know how to interpret 

 the radialis internus and, as I suppose, its homologue the tibialis 

 posticus, but I think that they may have been formerly real 

 flexores digitorum. 



A question of great importance is, on which bones of the hand 

 and foot are muscles inserted and on which not ? I will answer 

 this question here : — 



Hand. Foot. Miiscles. 



(1) " True " carpal bones, — proximal row — tarsal bones: no insertion, 



except pisiform except calcaneum : no origin. 



(2) Carpal bones — distal row — tarsal bones : no insertion.^ 



(3) Pisiform " Pm." calcaneum : insertion and origin. 



(4) Prsepollex prsehallux : only origin. 



(5) Metacarpal bones metatarsal bones : insertion and origin. 



(6) Phalanges: only insertion, no origin. 



Or in the form of a table (+ = present, 0=absent) : — 



Insertion. Origin. 



(1) True carpal and tarsal bones, proximal 



row 



(2) True carpal and tarsal bones, distal 



row + 



(3) Pisiform, calcaneum .... + + 



(4) Praepollex, praehallux + + 



(5) Metacarpal and metatarsal bones .... + + 



(6) Phalanges + 



Therefore I conclude, if in our subject the muscles are true 

 guides as to the homology of bones (and I do not doubt it), that 

 neither the pisiform and calcaneum (as Gegenbaur and others have 

 supposed long ago) nor the so-called praepollex and praehallux are 

 true carpal and tarsal bones, but that they have the same rank 

 and position as the metacarpal and metatarsal bones. If other 

 authors prefer to call bones on which is an insertion and an origin 

 of a muscle a '■^sesamoid bone," then they ought also to call the 

 metacarpal and metatarsal bones (which may be often reduced and 

 very small ossicles) " sesamoid bones." 



Further evidences for my view on the praepollex and praehallux 

 are the following : — 



The bones I call Pp. and Ph. are generally present everywhere 

 in all orders and families of mammals which have five true digits. 



These bones have everywhere the same situation on the radial 

 and tibial border of the hand and foot, and almost the same 

 relations to the smTOunding parts. 



In some animals there are distinct pads on the apex of Pp. and 



* The insertions of the tibialis anticus and posticus are not really on tarsal 

 bones, but originally either on digits or on the free bone or bones of the 

 border of the foot. 



Peoc. Zooi. Soc— 1894, No. XXV. 25 



