88 GROWTH 



that if these green foods are dried, or cooked for too long a 

 time, they lose their antiscorbutic effect. Another important dis- 

 covery 29 was made in Hoist's laboratory, namely, that if the 

 grains were germinated before being fed, they regained anti- 

 scorbutic potency. Since then the subject has been greatly ex- 

 panded, and the antiscorbutic potency of practically all common 

 foods has been determined. 



The last of the so-called deficiency diseases to be mentioned 

 is rickets, and it too has a long and distressing history. If we 

 leap into the last few years, we may say it is now believed to be 

 due to a disturbance in mineral metabolism. It is preponderat- 

 ingly a disease of the growing organism, though it has its 

 analogy in the adult also. The net result of the pathological 

 condition is the failure of normal deposition of calcium salts in 

 the bones. This is shown by the abnormally low content of salts 

 in the bone, the softness of the bones, and distortion from the 

 normal conformation. The most striking abnormality is shown 

 in the growing region where the maladjustment presents a char- 

 acteristic microscopic picture. The visible evidence of rickets is 

 usually accompanied, and usually preceded also, by a reduction 

 of the content of inorganic phosphorus, and frequently of cal- 

 cium, in the blood serum. 



As to the occurrence of rickets, it seems to be distinctly a 

 disease of civilization, both in man and in animals. It is most 

 prevalent where the population is most dense and where living 

 conditions are most unfavorable, that is in cities, and among 

 the poorer classes. So far as our information goes it is practically 

 confined to Europe and to North America. It is absent from the 

 oriental, tropical, and arctic countries. Savages and wild ani- 

 mals are free from the disease, but domesticated animals are 

 very subject to it, though various species differ in their suscepti- 

 bility. Precise evidence as to its incidence is difficult to obtain, 

 but Schmorl 30 has stated that over 90 per cent of the children 

 under four years of age that died in Dresden, between the years 

 1 90 1 and 1906, gave evidence of rickets. In this country Hess 31 



