J. Playfair McMurrich 191 
which of these possibilities is correct, although I am much more inclined 
to favor the second than the first. 
However that may be, I feel confident that in the radialis and ulnaris 
portions of the flexor communis digitorum we have the representatives 
of the palmaris profundus and that these muscles are the only represen- 
tatives of the profundus. The remaining portions of the flexor com- 
munis, together with the palmaris longus, represent the palmaris super- 
ficialis, and it is interesting to note that the mammalian muscles have 
the same relations to the elbow joint, so far as their general origin is 
concerned, as those of their reptilian prototypes; there has been, in 
other words no skipping across the joint of the profundus group of 
muscles. 
For the remaining muscles the homologies are less complicated. The 
flexor carpi radialis is equivalent throughout all the forms under consid- 
eration; the pronator radii teres, which in the majority of mammals 
lacks the coronoid head, seems undoubtedly equivalent to the reptilian 
muscle of the same name; this is also true for the epitroehleo-anconeus, 
which, it may be remarked, is, as Leche (1898) has suggested, a member 
of the flexor group and not one of the extensor series with which it has 
usually been classified. The flexor carpi ulnaris presents a slight diffi- 
culty, it being a question whether it represents the compound muscle 
so named in the reptilia, or merely the lateral head of that muscle. 
The double origin of the mammalian muscle, which is usual, seems to 
indicate that it is the equivalent of the entire reptilian muscle, in which 
case we have further evidence that a portion of the R. superficialis medi- 
alis is included in the mammalian ulnar nerve. 
Tabulating the homologies stated above we get the following results: 
Amphibia. Reptilia. Mammalia 
Ulno-carpalis ? ? 
Epitrochleo-anconeus Epitrochleo-anconeus Epitrochleo-anconeus 
Flexor carpi ulnaris Flexor carpi ulnaris Flexor carpi ulnaris 
(lateral head) (lateral head) 
( Flexor carpi ulnaris, Flexor carpi ulnaris 
| (medial head) (medial head) 
{ Palmaris longus 
Palmaris superficialis 4 ee | Portio condylo-radialis 
| Palmaris superficialis \ Portio condylo-ulnaris 
Bee prerundus Wy t ppeconator radii teres Tae ones 
Palmaris profundus IT Palmaris profundusII, III ) ¢ Portio ulnaris 
Palmaris profundus I ‘ ; ae her 
Palmaris profundus I { ( Portio radialis 
: J Pronator quadratus 
Pronator quadratus Pronator accessorius 
Flexor carpi radialis Flexor carpi radialis Flexor carpi radialis 
Pronator quadratus 
The results which I have recorded above differ materially from those 
obtained by Eisler (1895) from the comparison of the mammalian mus- 
