vi. effects of deficiency 231 



9. Histological Changes in the Ricketic Bone 



The following description of the micio.scopie changes of the costochondral 

 junction and adjoining areas of the ricketic rat is condensed from the dis- 

 cussion by Pappenheimer.^^ 



The zone of proliferating cartilage does not differ greatly from the normal 

 in extent or in arrangement of its cells. It is difficult, however, to define the 

 boundaries of this zone, owing to the lack of calcification in severely ricketic 

 bones. When there is lateral swelling of the cartilage the columns of cells 

 are separated by an excessive amoinit of matrix. 



In the zone of preparatory calcification are found the most pronounced 

 changes. There is a complete lack of calcification, and the depth of this 

 zone is greatly increased. In the normal rib there is little variation in the 

 depth, and it seldom exceeds four or fi\'e cells, whereas in the ricketic rib 

 the depth may be fifty cells or more. The extent to which this zone is 

 enlarged depends upon the length of time that the animals have been on the 

 ricketogenic diet and the extent of growth. If no growth has taken place 

 diu'ing the time on the experimental diet, there is but little enlargement of 

 this zone. In general, the more the animal grows, the greater the depth of 

 this zone, but usually this enlargement is one of the most dependable char- 

 acteristics of rickets. It has been frequently observed that ricketic lesions 

 are more severe in animals that do show definite growth diu'ing the period 

 on the ricketogenic diet. This is true in spite of the fact that vitamin D is 

 necessary for continued growth, as previously discussed. The arrangement 

 of the cartilage cells in the columns is usually maintained in the basal 

 portion of the zone of preparatory calcification, but toward the diaphysis 

 this arrangement of the cells is entirely lost, and there is considerable 

 variation in the size and shape of the cells. The uncalcified matrix takes on 

 the appearance of osteoid tissue which forms a considerable portion of the 

 metaphysis, particularly surroiniding the perforating vessels. 



After 4 weeks on the ricketogenic diet there is formed an excessive amount 

 of calcium-free osteoid tissue in the region of the primary spongiosa. The 

 arrangement of the trabeculae is no longer orderly, but instead they are 

 broad, con\'oluted masses of osteoid several times thicker than normal 

 trabeculae. Their relation to the original trabeculae is completely obscured. 

 Some of the osteoid masses contain a core of calcified tissue, but many 

 others show no trace of calcification. The osteoid is usually homogeneous 

 and stains evenly and deeply with eosin. The demarcation between osteoid 

 and calcified tissue is always very sharp. 



The i)erichondral osteoid of the ricketic rib is entirely free from calcifica- 



6» A. AI. Pappeiiheinier, ./. Ezptl. Med. 36, 335 (1922). 



