J. Playfair McMurrich 199 
condylo-ulnaris, the portion to the fifth digit, however, being derived from 
the palmaris longus. In the opossum but a small portion of the condylo- 
ulnaris is devoted to the formation of the sublimis, the contribution is 
distinctly greater in the cat and the entire muscle is taken up into it 
in the mouse. | 
Having then some indication of the line which the differentiation of 
the sublimis follows, we may now turn to the table given by Windle 
(1890) and inquire whether it reveals any further differentiation along 
the same line. And first of all we may consider his account of the’ 
the arrangement in the rat. The condylo-ulnaris is stated to be absent 
in this form, while the other four portions of the flexor mass are recog- 
nizable, and the sublimis is indicated as being an independent muscle. 
This may with propriety be interpreted, on the basis of what I have 
found in the mouse, that the condylo-ulnaris has been completely taken 
up into the sublimis, and, applying the same interpretation to other 
forms tabulated by Windle, we find that the same condition obtains in 
the majority of the rodentia. Proceeding to higher forms we find that 
in Cebus capucinus the condylo-ulnaris is again wanting and that, fur- 
thermore, the sublimis is closely associated with the condylo-radialis, 
that is to say, the sublimis not only includes the whole of the condylo- 
ulnaris but also receives a contribution from the condylo-radialis. The 
same condition occurs also in Cynocephalus maimon, with the addition 
that in this form the centralis has also disappeared, having, I imagine, 
been taken up into the sublimis. This disappearance of the centralis 
is also noted for several other monkeys, although in these no mention 3s 
made of any association of the condylo-radialis with the sublimis, and, 
finally, in the orang, it is stated that not only are the condylo-ulnaris 
and centralis wanting, but this is also the case with the condylo-radialis, 
the sublimis at the same time having a radial origin. 
The condition in the orang is essentially the same as in man and we 
may now see what a study of sections of a human arm reveals, my prepa- 
rations being made from an embryo of 4.5 em. Instead of being absent 
in part all the five portions of the flexor mass can be readily distinguished 
(Fig. 8), and on tracing them downward it is found that the condylo- 
ulnaris, the condylo-radialis and the centralis unite together to form the 
fiexor sublimis; the ulnaris is the flexor profundus and the radialis 
the flexor longus pollicis. In other words instead of the three condylar 
portions of the flexor communis being absent or only occasionally present 
as anomalies in man, they are always present and are incorporated in the 
flexor sublimis. Windle maintains that the condylo-radialis is repre- . 
sented by the second or ulnar head of the flexor longus pollicis; this IT 
