S44 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL VI. 
Chimpanzee, Hylobates, Circopithecus and Macacus it parts into two 
tendons—one for the trapezium, and the other for the middle phalanx 
of the thumb. Huxley describes the two divisions of the extensor 
ossis metacarpi pollicis in all four anthropoids, although he says the 
division is not so definite in the Orang as in the others.' Brooks? 
states that the sesamoid bone is apparently developed in all anthro- 
poids in the tendon of the extensor ossis metacarpi pollicis. The 
double insertion of this muscle into the trapezium and the first meta- 
carpal bone is frequently found as a variation in man, whilst the occur- 
rence of the sesamoid bone in the tendon of the muscle in question in 
man has been reported by Zuckerkandl.* 
The occurrence of the sesamoid bone in the tendon of the extensor 
ossis metacarpi pollicis has considerable interest attached to it, as Fick 
has suggested,’ that it represents a prepollex rudiment. The proba- 
bility is that the ossicle occurs very constantly in the Orang, although it 
may be of very small dimensions as Fick® found in a second Orang 
dissected by him, where it was scarcely the size of a grainof rice. Thus 
it may be very easily overlooked, and requires to be searched for with 
considerable care. The occurrence of this bone in the tendon of the muscle 
in question is no new discovery, as it is mentioned and figured by Vrolik® in 
the Orang,and the same writer states that it had been described by Camper 
in that animal. Camper looked upon it as a ninth carpal bone. Fick is 
inclined to believe that it does represent a supernumerary carpal bone. 
He has found it appearing as such in the skeleton of an old female Orang 
in the Leipzig Zoological Institute, where, on both sides it is attached 
to the carpus, on the one side being attached by some connective tissue, 
still unmacerated, to the trapezium, and on the other side lying between 
the trapezium and the scaphoid. There has been a great deal of dis- 
cussion concerning the occurrence of marginal structures in connection 
with the hand, held by some to represent additional digits, and desig- 
nated in the hand the preepollex and the postminimus. Similar obser- 
vations are made concerning the foot. The question is, whether or not 
we have evidence that the pentadactyle type of hand was derived from 
the heptadactyle type. The difficulty in determining the significance 
t Loe, cit., Vol. I, p. 596. 
2 Loc. cit., p. 81. 
3 Zuckerkandl. Discussion on Pfitzner's Paper, “‘ Bemerkungen zum Aufbau des Menschlichen 
Carpus.” WVerhandlungen der Anatomischen Gesellschaft. Géttingen, 1893, p. 193. 
4 Loc. cit. 1, p. 25. 
5 Loe. cit. 2, p. 208. 
6 Loe. cit., p. 13, (and Plate VI, Fig. 2). 
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