498 DR. V. I. FOESYTH MAJOR ON 



From the description j^iven by Dobson, it becomes quite evident that from the distal 

 end of this l)one there arise tendons for the fonr digits, so that we have here a bone 

 functioning as the commoTi tendon of the flexor digit, prof. Fronr this, however, it does 

 not necessarily follow that it is an ossified tendon. (The pisiform of Man is imbedded 

 in the tendon of the m. nlnaris internus ; but scarcely any anatomist will to-day 

 persist in considering it to be a tenontogenous sesamoid. It has been degraded to 

 play the part of a " sesamoid " *, and that only in Man and some of the Anthropo- 

 morpha.) 



Dobson has figured the volar aspect of the carpus of a Chrysochloris Trei-ehjaiii^, in 

 which the alleged ossification of the m. flexor prof, tendon has been removed. Here we 

 see. uhiad from the lunar, the flattened face of a bone [us.), which is not referred to in 

 the text; in the explanation of pi. xiii. fig. 5 it is termed the "ulnar sesamoid." Carus J 

 luxs seen and described this ossicle, and so have D' Alton sen. & juu. § The first-named 

 states that the " ossified tendon " starts (" ausgeht ") from it ; both Cams and the D'Altons 

 call it a pisiform (" Erbsenbein") ; but, so far as 1 am aware, later autliors, with 

 the exception of Dobson, have overlooked it. 



In a skeleton of Chrysochloris aurea, this so-called sesamoid articulates dorsad with 

 the ulnare, dorsad and radiad with tlie lunar, proximally with the ulna, volad and distally 

 with the " flexor dig. prof, ossification." The latter shows at the dorsal side of its distal 

 base two facets, the larger ulnad one for tlie " ulnar sesamoid," the smalhn- radiad for a 

 volar and distal projection of the lunar. 



I take this " ulnar sesamoid " to be the ossiciilum Daubentonii, viz. the basal part of 

 the pisiform ; but, owing to the distorted condition of the Chrysochloris carpus — 

 the lunar articulates with both radius and ulna— and from my insufficient material, 

 w^hich consists in a single skeleton of one of the smallest species, I cannot state my case 

 with greater certainty. If my vie\v is correct, then the " tendon ossification " is in all 

 likelihood the homologue of the distal part of the pisiform of other Mammalia, where it 

 very often starts backward at right angles from the long axis of the limb, sometimes, 

 as in Hylobates ||, directly downward, and sometimes more or less upward, viz. in 

 a proximal direction [Talpa). Which is tlie primitive direction I cannot for the 2iresent 

 decide. The Chrysochloi'idae vary so much from one species to the other that Cope 

 has divided them into three genera % ; and we may hope that it will be possible to settle 

 the question of the homology of this curious bone when the skeletons of these diff'event 

 forms shall have become available for comparison. 



It appears to me that the distal part of the pisiform will prove to be a remnant of a 

 lateral ray, which only secondarily entered into connection with the ulnare and the ulna. 

 Of this lateral ray the other accessory distal elements of Bathyergus, Cieiioii/ys, Mm, and 



» n 



' Das Pisiforme spielt . . . die Uolle eiiics in der Sehne des Miiskols (Jlexor curpi idnaris) bcfindlicheu Sesani- 

 beiijs," (jegenbauv, Lehrbuch d. Anatomie des Menschen, 6tc Autl. i. p. 422 (Ifidit). 

 t 'A Monograph of the Insectivora,' pi. xiii. fig. ii (lS8l!). J L. c. 



§ E. D'Altou d. Ae. und E. D' Alton d. J., ' Die Slielete dor Chiropteren und Insectivoreii," p. 22 (1831). 

 \\ Kohlbriigge, /. c. fig. 10. 

 ^ ' Araei-ican Naturalist,' xxvi. p. 126, footnote 1 (1892). 



