494. The Phylogeny of the Palmar Musculature 
abductor pollicis and is strengthened by the origin of the muscle from 
the volar surface of the annular hgament, by its not unfrequent confu- 
sion with the flexor brevis pollicis (sens. str.) and by its nerve supply 
from the median. 
7. The opponens pollicis is clearly allied very closely to the abductor 
and in all probability has the same derivation. Its occasional intimate 
union with the flexor brevis pollicis (sens. str.) is important in this 
connection as is also its supply from the median. 
& The lumbricales——The equivalency of these muscles to the super- 
ficial stratum of the flexor brevis medius of the reptilia has already been 
noted. In the two hands from different human embryos which I studied 
I found the lumbricales possessing their usual origins, 7. e. the first and 
second from the radial sides of the profundus tendons of the second and 
third digits, and the third and fourth from the adjacent sides of the 
third and fourth and fourth and fifth tendons, the muscles making their 
appearance in sections just at the point of separation of those tendons from 
the common tendon. In none of the muscles could any certain existence 
of doubling be distinguished. In the embryo of 6 cm. the four muscles 
were inserted into the radial side of the proximal phalanges of the four 
inner digits, but in one of 4.5 cm. the third lumbrical divided just before 
its termination into two equal ships which were inserted respectively into 
the ulnar side of the proximal phalanx of the third digit and the radial 
side of the corresponding phalanx of the fourth digit. 
The recent observations of Kopsch (1898) and Reinhardt (1902) 
have shown that the insertion of the third lumbrical into the adjacent 
sides of the third and fourth digits is of frequent occurrence, Kopsch 
finding it in 47 out of 110 cases examined (42.7 per cent) and Reinhardt 
in 43 cases out of 100. A satisfactory explanation of this variability has 
not yet been advanced. Von Bardeleben (1900) has suggested an associa- 
tion of the double insertion with a nerve supply of the muscle from both 
the median and the ulnar nerves, and in another place (1901) he has 
also suggested its possible reference to the doubling of the muscle seen 
in some of the lower mammals. As regards the first suggestion it may 
be noticed in the first place that it is rendered very plausible by the fact 
that Brooks (1887) found in twenty cases a double supply of the muscle 
in nine; Brooks’ paper, however, contains no statements as to the mode 
of insertion of the muscle in the various cases, and, furthermore, I have 
been able to determine with certainty that in the embryo with a double 
insertion mentioned above, the muscle is supplied by a twig from the 
deep branch of the ulnar and by that alone. 
