EFFECTS ON THE SKELETON 149 



As noted in the discussion of the etiology of rickets in Chapter V, the more 

 recent work on experimental rickets has recognized a vitamin factor. Elliot, 

 Crichton, and Orr ('22), however, produced rickets (with excess osteoid) in 

 pigs on diets of oatmeal and bran, in spite of abundance of vitamins A, B and C, 

 but preventable by the addition of calcium salts. Mellanby ('19, 21) has espe- 

 cially emphasized the importance of vitamin A, or an allied antirachitic factor, 

 though recognizing also other factors. By various deficient diets, he has pro- 

 duced in puppies skeletal lesions which appear in all respects essentially identical 

 with thosejof human rickets. Similar success has been obtained with experi- 

 mental rickets in rats by Korenchevsky ('21, '22, '22a), Sherman and Pappen- 



p IG 24. — From a photograph of a portion of a section of the upper extremity of the tibia. 

 Albino rat (McCl 14.2) had been placed on a phosphorus-poor diet (white flour, 93 per cent; 

 spinach, 1 per cent; NaCl, 2 per cent; lime, 2 per cent; yeast 2 per cent) for 1 month, beginning 

 at 3 weeks of age, resulting in severe rickets. Final body weight, 31 grams. Compare with 

 Fig. 53, and note the great hypertrophy of the epiphyseal cartilage (C), to the left of which is a 

 thin black band, representing the remnant of calcified bone layer of the epiphysis, surrounded 

 by a light band of uncalcified osteoid tissue. (The epiphyseal marrow cavity appears black.) 

 To the right of the epiphyseal cartilage, the zone of enchondral ossification is replaced by 

 a wide irregular zone (Z), representing the "metaphysis," composed of osteoid tissue, invading 

 marrow, and remnants of cartilage. The calcified bony trabeculae (shown in Fig. 53) have 

 nearly disappeared, but some remnants (T) are still visible. Around and between the slender 

 calcified trabeculae are relatively wide bands of uncalcified, osteoid tissue (0). The dark area 

 below and to the right represents marrow of the diaphysis. Von Kossa's silver method (calcified 

 tissue black). X50. (Preparation by O. J. Morehead.) 



heimer ('21), Pappenheimer, McCann, Tucker and Hess ('21), McCollum 

 Simmonds, Shipley, and Park ('21, '21a, '22), McCollum, Simmonds, Parsons, 

 Shipley and Park ('21), Shipley, Park, McCollum and Simmonds ('21, '21a, '22), 

 McCollum, Simmonds, Kinney, Shipley and Park ('22), Park, Shipley, McCollum 

 and Simmonds ('22), McCollum ('22), Shipley ('22), Hess ('22), Jobling, 

 Pappenheimer and Hess, ('22), and Pappenheimer, McCann and Tucker ('22). 



The characteristic histological changes produced in the bones of young 

 albino rats by experimental rickets are shown in Figs. 53 and 54. 



As previously noted, the work of McCollum and his co-workers strongly 

 indicates that at least two factors are concerned in the production of rickets: 

 (1) a "fourth vitamin" or organic factor which is closely associated with 

 vitamin A and promotes calcium deposition; and (2) a dietary deficiency of 



