OSTEOPOKOSIS AND OSTEOMALACIA. 
319 
In the pathological anatomy, osteoporosis is described as 
consisting of a widening in the Haversian canals, through an 
atrophous process which absorbs the innermost portion of 
the same ; by this process the fundamental substance degen¬ 
erates into a cancellated formation, which is difficult to dis¬ 
tinguish from the normal cancellated tissue of the bone. 
1 his atr ophy is either concentric or eccentric, according as the 
process of resorption proceeds toward or from the axis of these 
vascular canals; and it is evident that such is only possible, 
after the bony substance has become of a soft consistency, 
through a hypermmic circulation. 
The appearance of a bone in which osteomalacia is pres¬ 
ent depends upon the length of time throughout which the 
bone has been the seat of the process. In the earliest stages 
theie is hypermmia; the vessels together with the bony 
(Haversian) canals are of larger calibre, but the tissue adja¬ 
cent to the latter is only in an insignificant degree altered. 
In cases further advanced the hypersemia is more con¬ 
siderable ; a transverse section of a bone from such a case 
shows numerous red points, with haemorrhages in the medul¬ 
lary substance. . The medulla is enlarged, and within it are 
noted small bony scales ; the bone is much easier cut than in 
health ; the lacuni (osteoplast) are enlarged and empty, their 
canaliculi have either totally or nearly disappeared, and the 
bone cells proper are in a thready, degenerated state. The 
whole presents a transformation of the bony matter into 
osteoides, and at last is seen one vast mass of cavernous sub¬ 
stance. In the severest cases the hypermmia of the bone 
and marrow are still more intense, the corticular portion be¬ 
comes more spongy, soft and tender; but the marrow, con¬ 
trary to the solid substance, increases and appears as a soft 
watery mass of a grayish-yellow color, which advances into 
the epiphesis, thereby so diminishing the strength that frac¬ 
ture is inevitable. The specific gravity of the bone has de¬ 
creased ; much of its calcium salt has disappeared,—indeed 
only one-half the original quantity may remain,—and con¬ 
temporaneous with this decrease in solids is an increase in 
the watery constituents. 
