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Show 1894.] MAMMALIAN HAND AND FOOT. 373 ("abductor prcehallucis"), but l a m 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 radicdis 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 haud and foot are muscles inserted and on which not ? I will answer this question here :- Hand. Foot. Muscles. (1) " True " carpal bones,-proximal row-tarsal bones: no insertion, except pisiform except calcaneum: no origin. (2) Carpal bones -distal r o w - tarsal bones : no insertion.1 (3) Pisiform "Pm." calcaneum: insertion and origin. (4) Praepollex prjeballux: only origin. (5) Metacarpal bones metatarsal bones: insertion and origin. (6) Phalanges: only insertion, no origin. Or in tbe form of a table (4- = present, 0=absent):- Insertion. Origin. (1) True carpal and tarsal bones, proximal row 0 0 (2) True carpal and tarsal bones, distal row 0 4- (3) Pisiform, calcaneum 4- + (4) Praepollex, praehallux 4- + (5) Metacarpal and metatarsal bones .... + + (6) Phalanges + 0 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 m y 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 surrounding parts. In some animals there are distinct pads on the apex of Pp. and 1 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. PROC. ZOOL. Soc-1894, No. XXV. 25 |
