352 DISEASE IN WILD MAMMALS AND BIRDS 
In so far as the deformities of the skeleton may serve 
to distinguish between rickets and osteomalacia, 1 can 
only point to the preponderance of changes in the skull 
and extremities in the former and of the trunk bones in 
the latter. Deformity of the chest, barrel-shape short- 
ening and pigeon breast, is due more to posture than to 
the essentially osseous changes. "Rachitic rosary" may 
occur in both, but it is always better exhibited in rickets ; 
in this disease the swellings occur at the costochondral 
junction, while in osteomalacia rosary-like nodules may 
develop anywhere along the ribs. 
Examination of the anatomical lesions is, however, 
somewhat more helpful, and the following description for 
osteomalacia may be contrasted with that already given 
for rickets. The peculiar change is a thinning of the shaft 
of long bones and reduction of the subperiosteal plates 
of flat bones. 
In mammals the long bones are more affected than in 
birds whose sternum, ribs and beak show the severest 
changes. The skull is frequently not affected to a serious 
degree, but may, however, show advanced lesions, the 
cranial plates being thinned in places so that they may 
be bent in, or occasionally a periosteal thickening may 
be found ; the head as a whole is not misshapen. The ribs 
are softened and may be of paper thickness although 
there may be found a periosteal overgro\\i;h, perhaps a 
kind of splinting, which makes the diameter variable. At 
costochondral junctions, beading may be found, but with- 
out the active congestion seen in rickets. Similar 
alterations may be found in the long bones, here in 
characteristic degree in that the shaft walls are thin, by 
removal of the endosteal and periosteal layers sometimes 
with definite retraction of the marrow. Occasionally sub- 
periosteal thickenings, made of osteofibrous tissue are 
encountered. At the epiphyses there are strands of 
gelatinous tissue, fibrous and cartilaginous, separating 
