1890 — 91 .] Drs Symington & Thomson on Defective Ossification. 281 
In circumference the shafts are quite normal. With scarcely an 
exception the shafts present very pronounced curvatures, which are 
in each case an exaggeration of the normal curve of the hone. The 
humerus is abruptly curved forwards in its lower half, the radius 
and ulna are uniformly curved, with the concavity on the flexor 
aspect. The femur is bent almost to a right angle at the junction 
of the shaft with the lower end, the angle being open posteriorly. 
The tibia is uniformly convex forwards, and the fibula backwards. 
The metacarpals and metatarsals have practically no shaft; they 
possess a minute central osseous nucleus, which is almost surrounded 
by the cartilaginous ends. 
The curvatures we have described do not appear to result, like 
those met with in rickets, from softness of the bones. The shafts 
are firm and rigid. We would suggest that they depend upon arrest 
of the cartilaginous ossification and consequent arrest of growth in 
the axial portion of the shaft, while the peripheral membranous 
ossification continues. 
Lastly, the secondary centres of ossification or epiphyses at 
the ends of long bones, which are normally present at birth, 
e.g., in lower end of femur and upper end of tibia, are entirely 
absent. 
The joints of the extremities have suffered in function in conse- 
quence of the alterations in the bones. They are disproportionate 
in size, and their movements are seriously restricted by the large 
size of the cartilaginous ends of the bones over which the ligaments 
are tightly stretched. Generally speaking, all the joints are fixed 
in the flexed position. 
The condition of the short bones of the extremities is similar to 
that of the short bones of the trunk. Those which are cartilaginous 
at birth are of normal size, e.g ., carpus. Those which have a central 
osseous nucleus at birth, e.g., astragalus, os calcis, but which do not 
depend for their growth on ossification proceeding from the nucleus, 
are also of normal size. The central nucleus, however, is distinctly 
smaller. 
The difference between the long and short bones is well illustrated 
by a longitudinal section of the foot passing through the great toe, 
the tarsus being found of normal size, while the metatarsals and 
phalanges are extremely short. 
