242 



VITAMIN D GROUP 



instead of taking a parallel course, are diverted and the cartilage is broken 

 up into une\'en tongues. Park points out that in the earliest cases the his- 

 tologist will find only in the fastest growing bone some thinning of an 

 occasional spicule, and an area here and there where calcification is entirely 

 absent from one of the main partitions in the cartilageJ^ 



As a result of the total or partial failure of the calcification in the matrix 

 substance of the cartilage, there is failure of support for the large cartilage 

 cells lying nearest the shaft. There results, therefore, the phenomenon of 

 compression of these cells which may be flattened out, or in severe cases 



Fig. 18. Vertical section of the proximal end of tibia, showing early changes at 

 the chondro-osseus junction. Focal defects in the calcification of the zone of pre- 

 liminary calcification. 



actually ruptured. Such compression is generally distributed in a spotty 

 maimer and is severe and generalized only in bones where there is rapid 

 growth, and in a child with severe rickets. In a severe case the spicules 

 surrounding the cells are bent and buckled so that they may actually lie 

 on their sides. Occasionally, the fractured spicules may be driven into the 

 cartilage. 



The continued proliferation of cartilage cells, without concomitant min- 

 eralization and ossification, results in the lengthening of the cartilage plate 

 and in swelling of individual cells. The increase in size of the cartilaginous 

 plate is not due to an increased production of cartilage cells, as proposed 

 by Ziegler.""* There is a normal production of these cells, but they fail to 



" E. Ziegler, Lehrbuch der Allg. Pathol. Anat. 2, 179 (1898). 



