954 Osteonialaeia. 



Pathogfenesis. Tlie commencement of the pathological 

 process in the bones is probably similar to that in rachitis 

 (see p. 937), whether the trouble be due to a lime deficiency 

 of the organism or to another cause. But since in this disease 

 the process occurs in fully developed bones, the later tissue 

 changes differ more or less from those in rachitis. In osteo- 

 malacia the peculiar proliferative processes are absent which 

 are noted in rachitis at the borders l)etween the epiphyses and 

 the diaphyses of tlie long bones, and on the other hand the 

 decalcification (osteoporosis) predominates over the new- 

 formation of osteoid tissue, at least in many cases. Still, ex- 

 ceptions are ol)served not very infrequently, in so far as a 

 decided proliferative process may set in under the influence 

 of certain mechanical factors (see p. 937) and of other agencies 



Fig. 165. Skeleton of the cow with osteomalacia, illustrated in Fig. 168. Tlic ribs 

 are bent forward, show multiple fractures, and callus formation. Both ilia are 

 fractured, the fractured ends being crowded into one another. Enormous callus for- 

 mation, moderate lordosis of the lumbar vertebrae ; callus fonnation at the base of 

 the spinal processes of the anterior dorsal vertebrae. 



that are not fully known. In other cases the new-formation of 

 osteoid tissue may be entirely lacking. 



The further consequences of the diminution in the firmness 

 of the bones and of the disturbances in the metal)olism are 

 the same as in rachitis (see p. 937), except that in osteomalacia 

 the bones are more often brittle rather than pliable. 



Relations of Rachitis to Osteomalacia. While Virchow and others 

 differentiated rachitis sharply from osteomalacia, still other authors 

 declared both diseases to be closely related, or identical. Indeed the 

 pathogenesis and the etiological agencies of both afifoctions agree in 

 many points, and it appears as though the anatomical or microscopical 

 differences were dependent solely upon the difference in the age of 



