1910—11.] Bone Growth in absence of Functioning Testicles. 135 
was enormous, and weighed close on 20 lib. in place of the normal 7-10 lib. 
Its long bones were most remarkable in shape. The shafts about their 
middle were of an approximately normal diameter, and then rapidly 
increased in size as they approached the extremities. The meaning of 
such an appearance is clear. It is that endochondral ossification has been 
responsible for the bulk of the bone, and that the rapid diametric increase 
of the bone shaft is due to the forced proliferation of the cartilage cells. 
When to this observation we add the fact that in a poorly nourished 
foetus the bones tend to be of a more uniform diameter throughout their 
length, there can be little doubt that a predominantly anabolic condition of 
metabolism is the direct stimulant of chondrogenesis, and this can only be 
explained on the lines of the metabolic interpretation of the histology of 
endochondral bone formation. 
These facts are readily demonstrated by means of measurements. By 
measuring a young and growing femur at its centre and at its ends it is 
easy to construct an index of cartilaginous expansion, for periosteal bone 
formation is in the foetus very slight, and any difference there may be in 
the diameter of the diaphysis of any long bone at its central point and at 
its end is due almost entirely to lateral expansion of the cartilage. The 
expansion is readily demonstrable microscopically as due to the great 
proliferation and hypertrophy of the cartilage cells immediately in front 
of the line of bone formation. 
The result of a series of measurements undertaken to demonstrate this 
point in connection with the differing shapes of the shafts of bones in thin 
and fat foetuses are shown in Table XL. 
Table XL. — Index of Cartilaginous Expansion in developing Femora. Com- 
parison of Diameter of the Central Part of the Diaphysis with that of 
its Extremity. 
Central Diameter =100. 
Diameter 
at Extremity. 
Diameter 
Mid-point. 
Index. 
mm. 
mm. 
Normal (average of ten 
Irish femora) 
731 
29-3 
249-4 
Normal (average of ten 
Irish foetal femora) . 
12 
4 
300 
Fat Foetus — 
No. 1 . 
14-5 
4-5 
322*2 
No. 2 
30 
9 
3333 
No. 3 . 
8 
2-2 
363-6 
No. 4 . . 
26 
6 
433-3 
Fat Baby 
47 
12 
391*6 
