VI. p:ffects of deficiency 



243 



undergo normal senescence and they accumulate, thereby causing a widen- 

 ing of the cartilage plate in the proliferative zone (Fig. 20). If the rickets 

 persists, however, the rate of proliferation of these cells diminishes, so that 

 in extreme cases dwarfism may result. Besides this basic cause of dwarfism 

 in extreme rickets, shortness of stature may be due to a bending of the 





% 





f #. 



^ 4P ■* ~ 



Fig. 19. High power of Fig. l.s, .siiuwing lirst muturation of cartilage cells with 

 disappearance of some of the cells at the chondro-osseus junction. Beginning irregu- 

 larity of the Vjlood vessels. Deficient, almost absent calcification in the zone of pro- 

 visional calcification. 



soft long bones, and accompanying fractiu'es with shortening, and also to 

 squashing of the metaphysis. 



The pattern of capillary invasion into the growing cartilage becomes 

 abnormal in two ways. In the normal bone, vessels invade the cartilage by 

 extension from the shaft only. In the ricketic bone, in addition to invasion 

 from the shaft, tiny blood vessels penetrate also from the epiphyseal end 

 and from the sides. The second abnormality is the type and formation of 

 the invading l)lo()(I vessels. In the normal cartilage the capillaries are seen 

 extending up from the shaft and pcMietrating the mati'ix walls between the 

 cell columns, and by depositing lime salts on to these partitions they create 



