152 THE VITAMINES 



animals find infected carcasses to eat. This condition is tested by 

 giving the animals rotten bones; if they chew these bones, then the 

 diagnosis of pica is verified. 



Cure of pica. To overcome pica, a mixed diet may be used which 

 will cure the disease in one month. Two pounds of wheat bran cures 

 it in three weeks, and 112 grams of bone meal is supposed to have 

 the same effect. Besides this, the addition of calcium phosphate 

 and sodium phosphate, and even phosphoric acid in drinking water, 

 may be used. 18 



Etiology of pica. As we have seen above, Theiler thought that 

 the chief cause of pica was the poverty of the diet in phosphorus, 

 accompanied perhaps by too much calcium, although it is admitted 

 that other dietetic factors also may play a role. Theiler also stated 

 that on analysis of the diet, the phosphorus was found within the 

 limits of the accepted standards for such animals. He concluded 

 therefore, that the accepted figures had to be revised. We know 

 from the study of deficiency diseases, that under such conditions 

 there is often a negative calcium and phosphorus balance, and it has 

 been stated from time to time, that the addition of phosphorus (we 

 refer only to phospho-cod liver oil, hypophosphites, etc.) may result 

 in a definite improvement. This may be the case with pica. The 

 animal perhaps has sufficient phosphorus in the food but is unable to 

 retain it because, we may say, the diet lacks vitamine A. An addition 

 of phosphorus, in whatever form, may perhaps lead to a temporary 

 improvement and, in the light of the modern conceptions of lamziekte, 

 may also protect against this disease, since the animals would not 

 eat the carcasses. But the cause of pica and the metabolic disease 

 may endure till the arrival of a better season and a recovery of the 

 vegetation. For it can be shown definitely that pica prevails only 

 at certain times of the year, when the vegetation thrives but poorly. 

 If this is so, then vitamines, as well as salts, may be lacking; a normal 

 vegetation should provide everything for the animal that is necessary 

 to life. The simultaneous development of undernutrition, in the 

 form of "poverty," and perhaps also stijfziekte, in lamziekte regions, 

 is illustrative of the profound dietetic deficiency of the local vegeta- 

 tion. As to the etiology of pica, this can be cleared up only by exact 

 investigation, especially by metabolism experiments. Such accurate 



18 In this connection it is interesting to compare the influence of phos- 

 phorus on pica with that on experimental rickets in rats (p. 327). 



