2'M\ Journal of the Department op Agriculture. 



All the cattle at Armoedsvlakte were tested once a week as iv 

 matter of routine, so that the effect of treatment and the seasonal 

 variation of craving could be plotted in the form of curves showing 

 the effect of the particular factor under investigation. Really 

 scientific records of osteophagia were thus obtained for the first time. 



The seasonal variation curve dates back to May, 1919, when 40 

 I)er cent, of all grazing animals admitted to the test showed craving. 

 There was then a gradual increase until 5th August, when the 

 maximum craving was reached, and 80 per cent, of all the cattle ate 

 rotten bones. From that date onwards a gradual descent in the curve 

 was noted, until 27th October, by which time the craving had again 

 fallen to 40 per cent. During this period the weather had been 

 continuously dry, but as it grew warmer the spring vegetation began 

 to appear, and this is regarded as responsible for the diminution in 

 pica. During the ensuing fortnight rain fell, the young vegetation 

 became almost luxuriant, and by the middle of November the craving 

 had rapidly fallen to 6 per cent, of all the animals tested ; had 

 vanished except for the more or less chronic cravers. 



This minimum ci'aving was maintained through a fortnight of 

 rainless weather, and then, as the young grass wilted, it rapidly 

 returned, reaching a maximum of 82 per cent, within three weeks. 

 For the next two months of drought it oscillated around this figure.- 



The craving curve, up to that date, therefore showed pionounced 

 craving while the cattle were grazing upon the old grass of the pre- 

 ceding rainy season, reduced craving as the young spring vegetation 

 began to shoot, practically no craving after the beneficial effect of 

 the rains upon the young grass, but a recrudescence of craving 

 during the ensuing drought when the young grass wilted and 

 shrivelled up — a craving which remained high so long as the drought 

 continued. 



In the middle of January, 1920, the drought broke, the pasture 

 rapidly recovered, and it was naturally thought that the craving would 

 again disappear. The unexpected happened, however, and notwith- 

 standing the ample supply of good green grass, and the absence of 

 wilting, the craving did not fall to the previous 6 per cent., but only 

 to 50 per cent. As the age of the grass advanced towards maturity, 

 the craving curve again rose, and by the end of March once more 

 stood at 80 per cent, of all the cattle tested. 



This behaviour was a little difficult to understand at first, but was 

 found to be correlateable with the phosphorus content of the growing 

 vegetation. We cannot yet offer a complete explanation of the precise 

 ]elationship between the wilting of the young grass and the rise in 

 the pica curve, but we hope to get further evidence next time the 

 phenomenon occurs. The general behaviour, however, can be satis- 

 factorily explained upon a phosphorus-deficiencj' theory which we 

 hope to elaborate finally as main factor in the explanation of pica ; 

 not necessarily as only factor, and not necessarily in the conven- 

 tionally accepted sense of a deficiency disease. In passing, it must 

 be made clear that any such hypothesis bears no relation to any sort 

 of deficiency theory for lamziekte per se, but bears only on the 

 correlated craving ; further, that it has nothing to do with 

 osteomalacia or osteoporosis or any other disease which has been 

 mixed up with lamziekte in the past and is confused with it still by 

 some recent authors. 



