112 
THE VOYAGE OF H.M.S. CHALLENGER. 
specimens in Humphry’s table was 100, and a similar mean was obtained by Flower. 
Iu the three gorillas measured by Humphry the mean index was only 77 "7 ; the mean 
of the three gorillas in Mr. St. George Mivart’s tables 1 was 81 ‘6, whilst Flower puts this 
index in the gorilla at 80. The index in the chimpanzee and orang is therefore very 
high, and expresses that the forearm closely approximates in length to the upper arm, so 
that they may be described as hyperdolichokerkic. In the gorilla, on the other hand, 
there is a much greater disproportion between the length of the radius and humerus, for 
the mean index is about 80. In this respect the Andaman Islanders and Fuegians surpass 
the gorilla in the relative length of the forearm to the upper arm, for the radio-humeral 
index in them averages between 80 and 82, so that in the proportion of forearm to upper 
arm they are probably the most ape-like of the races of men. Europeans again are at 
the opposite end of the series, for the mean radio-humeral index in them did not reach 
75, whilst the Australians, Kaffirs, Negros, &c., form an intermediate series. 
The tibio-femoral index in my three chimpanzees ranged from 81 to 83 '5, and the 
mean was 8 2 A. Professor Humphry’s four specimens gave a mean 80 '6. In my single 
orang this index was 86, and the mean of Humphry’s two specimens was 86'8. His 
three gorillas had a mean 81, and Mr. Mivart’s specimens had the same index. In 
Europeans this index is about 82, whilst in the Australians, Negros, Andaman Islanders, 
and Fuegians it was higher, and ranged from 83 to 85 or 86, according to the mode of 
measurement adopted. The difference therefore in the relative length of the tibia to the 
femur in man, as compared with the chimpanzee and gorilla, is not very marked. In the 
orang, however, the index rises considerably, owing to the greater proportional length of 
the tibia, and it is also to be noted that in the lower races of men there is a rise in this 
index as compared with Europeans, so that as regards the proportion of leg to thigh they 
are more in accordance with what is found in the orang. 
The femoro -humeral index in my three chimpanzees ranged from 94 to lOO'S, with a 
mean of 977, so that the humerus sometimes exceeded the femur in length. The mean 
index computed from Humphry’s measurements of four chimpanzees was 98, and Flower 
places it at about 100. In the orang the humerus is much longer than the femur, and 
in my specimen the femoro-humeral index was 133'4, the mean of Humphry’s two 
specimens was 132, and Flower gives it as 130. In the three gorillas measured by 
Humphry the humerus was longer than the femur, though not in the same proportion 
as in the orang, and the mean index was 119 ; in Mivart’s specimens the mean index was 
also 119, and in Flower’s 120. There is thus a considerable range of difference in the 
relative proportions of femur to humerus in the great Anthropoid apes, for, whilst in 
the orang and gorilla the humerus considerably exceeds the femur in length, in the 
chimpanzee these bones are almost equal and as a rule the femur is somewhat longer 
than the humerus. 
1 On the Appendicular Skeleton of the Primates, Trans. Roy. Soc. Lond., 1867. 
