THE PHYLOGENY OF THE PALMAR MUSCULATURE. 
BY 
J. PLAYFAIR McMURRICH, Ph. D. “ 
From the Anatomical Laboratory of the University of Michigan. 
WitH 11 Text FIGURES. 
Writing in the nineties of the nineteenth century, Leche (1893) intro- 
duces his account of the intrinsic muscles of the mammalian hand with 
the following words: ‘“ Da die myologische Literatur noch keine Mater- 
ialen enthalt, welche fiir eine vergleichende oder auch nur zusammen- 
fassende Darstellung der Handmuskulatur geniigt, und da ausserdem 
die Nomenclatur der verschiedenen Componenten dieser Muskelgruppe 
ausserordentlich schwankend ist, halte ich es fiir das Geeignetste eine 
rein descriptive Darstellung der wichtigeren Befunde bei den verschie- 
denen Siugethierordnungen zu geben.” Although this indictment 
may not in all its particulars be as pertinent now as it was, there are 
still remaining for solution many questions concerning the fundamental 
plan of the mammalian hand muscles and their phylogenetic signifi- 
cance, and the following pages record an attempt to diminish the num- 
ber of these. 
In a previous paper (1903), in which the flexor muscles of the forearm 
were considered from the phylogenetic standpoint, I showed that the 
flexor sublimis digitorum had been evolved by the union of certain por- 
tions of the antibrachial flexor mass, which primarily terminated at 
the wrist joint, with the most superficial layer of the intrinsic hand 
musculature, part of the latter undergoing degeneration to form the 
terminal portions of the tendons. The profundus tenilons, on the other 
hand, were evolved from a deeper layer of the palmar aponeurosis and 
the lumbrical muscles represent a layer of palmar muscles which origin- 
ally arose from that aponeurosis. I did not attempt, however, in that 
paper, a complete reconstruction of the history of the palmar muscula- 
ture, and I now propose to correct that omission as far as possible by 
recording the results of a comparative study of the palmar musculature 
of the same series of forms as were employed in the earlier paper. 
These results are based mainly on the study of serial sections. 
