244 THE VITAMINES 



From what has been said, we see that universal rules as to the 

 stability of the vitamines cannot be formulated. Every single case 

 must be investigated separately, since we do not yet know of any 

 rule for determining the stability or lability of these substances. 

 Evidently, the vitamine content of foodstuffs prepared for ingestion 

 depends considerably upon its original content in the natural state. 

 This original content may vary with the country in which it is 

 produced, with the condition of the soil, the climate and so on. 

 This is true to our primary sources of vitamines. As for the second- 

 ary sources, animal products, the question is much more complicated 

 and depends, for the most part, upon known factors, but partly 

 upon unknown factors too, which we have already discussed. 



CEREALS 



Under this heading we shall describe not only the cereals, such as 

 wheat, barley, rye and maize but also the breadstuffs. Although an 

 etiological relationship between the refining of cereals for human 

 consumption and beriberi has been suspected for a long time, and in 

 fact demonstrated, the economic conditions arising out of war have 

 stimulated interest in the question and in established knowledge on 

 the subject. In almost all countries, the investigators have endeav- 

 ored to utilize the nutritive value of cereals to the best possible 

 advantage. To the problem of the economic utilization of the grain 

 kernels, another factor is added which we have already noted in the 

 etiology of avian beriberi, namely, that in most cases, vitamines A 

 and B are localized in a certain portion of the kernel. Because of 

 this, modern refining may result in a more or less complete removal 

 of these essential factors. It is indeed true that under normal con- 

 ditions, when the population eats other foodstuffs, in addition to 

 bread, there is no immediate danger of an avitaminosis, and yet we 

 must remember that at present bread may constitute a large per- 

 centage of the diet. Although whole wheat bread is used almost 

 exclusively in many countries, in more cultured sections, white bread 

 is used in preference. Aside from the aesthetic factor, some scientific 

 facts are known which make it desirable to mill the grain. One of 

 the reasons frequently cited is the fact that flour from whole wheat 

 keeps with greater difficulty. In fact, the whole grain, very rich in 

 fat, is very difficult to store. The polishing of rice is often defended 

 on these grounds, and Ottow (I.e. 518) proposed measures for increas- 



