Is there More than One Kind of Rickets? 151 



of human beings. The costo-chondral junctions were greatly en- 

 larged; in some animals the thoracic wall was sunken at the sites 

 of the costo-chondral junctions and the shafts of the ribs were 

 fractured. The long bones of the extremities were enlarged at 

 the ends; they could be cut and broken easily. Between shaft 

 and cartilage lay a yellowish zone two to three mm. deep, the 

 rachitic metaphysis. The proliferative cartilage extended in ir- 

 regular prolongations toward the shaft. Calcium deposition in 

 the cartilage was entirely lacking or extremely defective. The 

 intermediate zone between cartilage and shaft presented the 

 picture typical of the metaphysis in the bones of rachitic children. 

 It was composed of cartilage in all stages of metaplasia or de- 

 generation into a material indistinguishable from the osteoid, 

 trabecular consisting of osteoid, blood vessels bordered by marrow 

 elements, scattered, irregular deposits of calcified material incased 

 in osteoid, and connective tissue. All were intermingled in a 

 disorderly manner. The trabecular of the shaft were surrounded 

 by broad investments of osteoid. 



When the diets of the second group (the calcium being deficient 

 the phosphorus at a level not far from the optimal and the calcium- 

 phosphate ratio low) were fed to rats kept under ordinary labora- 

 tory conditions (room light), there developed a diseased condition 

 of the skeleton which also bore marked resemblances to the lesions 

 found in the rickets of human beings. The gross deformities 

 caused by the second group of diets were as great or greater than 

 those caused by the first group and corresponded exactly to the 

 deformities found in rachitic children. The thorax was even more 

 deformed than in the rats fed the diets of the first group; it was 

 flattened from side to side and marked at the sides by deep grooves 

 following the costo-chondral junctions; the angular deformities 

 produced by the costal cartilages and the shafts projected into 

 its interior ; the costo-chondral junctions were enlarged and greatly 

 distorted; fractures in the shafts of the ribs were especially 

 numerous. The lower ends of radius and ulna were enlarged as 

 were also the ends of all the long bones of the extremities. The 

 bones were extremely soft and weak. Between the cartilage and 

 the shaft was a white intermediate zone one to three mm. deep. 

 Microscopic examination showed that the cartilage was entirely 



