RACHITIS. 559 



and after the seventh yjar, it is far more rare. In some families, the 

 tendency to it appears to be hereditary. Improper nutrition of chil- 

 dren is undoubtedly the most frequent cause of the disease. I also 

 believe that the gastric and intestinal catarrh, due to the improper nu- 

 trition, greatly favor the occurrence of the disease, although I do not 

 consider it as proved that this results from reabsorption of the lactic 

 acid. The occurrence of rachitis in well-nourished children, with un- 

 impaired digestion, shows that, besides the above, there are some 

 other unknown causes of the disease. 



ANATOMICAL APPEAKANCES. For the histological details of the 

 examination of rachitic bones, I refer to the works of Virchow, Kolli- 

 Jeer, and JZ Mayer. Virchow enumerates the changes observed in 

 the epiphyseal cartilages during rachitis as follows : 1. Arrest of the 

 line of ossification while the preparatory line of proliferation of the 

 cartilage relatively increases. 2. Encroachment of the medullary space 

 into, or even beyond, the line of ossification, while the proliferation of 

 cartilage continues. 3. Formation of fibrous medullary spaces, osteoid 

 transformation of the parts around them, as well as of distant parts, 

 with calcareous deposits. The processes observed in the diaphyses are 

 grouped as follows, by Virchow : 1. Greater density of the periosteal 

 proliferation, with progressive rarefaction of the substance in the 

 areolae and cancellated tissue. 2. Deficient ossification of the cancel- 

 lated tissue, and continuance of the deep layers of compact exterioi 

 substance. 3. Partial formation of cartilage in the areolas. 



The clumsy appearance of rachitic bones and the swelling of the 

 epiphyses are sufficiently explained by the proliferation of the perios- 

 teum and epiphyseal cartilages. The epiphyses are thickened and not 

 elongated, according to Virchow / not because the proliferation is 

 chiefly lateral, but because the soft proliferating layers are compressed, 

 and deflected laterally by the weight of the parts pressing on them, 

 and by muscular action. The distortions of rachitic bones depend 

 partly on curvatures, partly on angular deformity. The curvatures 

 occur chiefly at the epiphyses and at the points of cartilaginous union 

 of bones which have no epiphyses, while the angular deformities occur 

 chiefly at the diaphyses. In the long bones of the extremities it often 

 looks as if the epiphysis had slipped past the diaphysis. Curvature of 

 the posterior ends of the ribs of one side of the thorax not unfre- 

 quently induces asymmetry or obliquity of the thorax. In many 

 cases the points of union between the anterior ends of the ribs and the 

 costal cartilages are bent inward, while the sternum, with the sternal 

 end of cartilages, is pressed forward. This deformity, pectus carina- 

 tum seu gallinaceum, is due to the softness of the parts mentioned, 

 they having lost the power of resisting the pressure of the atmosphere 



