190 Proceedings of Royal Society of Edinburgh. 
The smallest embryo in which all three phalanges were more or 
less completely fused was 60 cm. in length. Figure III. represents^ 
a longitudinal section through the distal portion of the second digit 
of the pes. This figure is an extremely important one. I have 
considered very anxiously and fully all the possible objections to 
my interpretation of the facts established, and, as far as I can see, 
the only possible criticism is that the cartilages I look upon as 
representing phalanges are only epiphyses. The section figured 
fully disposes of this criticism. It shows the ossified distal end of 
the shaft (s) of the second metatarsal supporting a cartilaginous 
epiphysis (e), which, when examined with a high power, presented 
all the characteristic appearances in a typical epiphysis. If this 
cartilage (e) is the epiphysis of the metatarsal, the piece of carti- 
lage (1) beyond must be something else. The piece of cartilage (1) 
cannot be an epiphysis, for an epiphysis is never articulated to 
its shaft ; it must, in fact, represent one or more of the phalanges 
of the second digit. Convincing proof of this is afforded by the 
presence of the joint at the end of the epiphysis. Dr Hepburn, 
who has made a special study of joints,* on seeing the specimen 
from which the drawing was made, without knowing anything of 
its origin, at once stated that it showed an arrested diarthrodial 
joint, ^.e., a joint which in an imperfect way resembled the joints 
of our fingers and toes. When first dissected there was free move- 
ment at the metatarso-phalangeal joint represented in the section, 
and when the capsule of the joint at the end of the fourth 
metatarsal was opened a droplet of fluid was seen to escape. 
That this is possible will be at once evident if the extent of the 
cavity of the capsule is taken into account. Hence it may be held 
as proved that, up to at least the sixth month of foetal life, the 
metacarpo-phalangeal and metatarso-phalangeal joints, though not 
w^ell formed, are quite distinct and functional. Figure IV. repre- 
sents the fourth digit of the manus in an eight-months’ foetus, 
figure Y. the same digit in a nine-months’ foetus, while figure VI. 
shows the condition of the second digit one month after birth. 
In figure IV. the epiphysis is now much shorter, and the shaft 
of the metacarpal (II.) is expanded at its lower end, and there is an 
indication of where the terminal phalangeal joint originally existed, 
* Journ, of Anaf. and Physiol., vol. xxiii. p. 507. 
