MINERAL METABOLISM 309 



marily necessary for the digestion or utilization of the foodstuffs, but 

 that their lack even over a brief period leads to unpleasant nervous' phe- 

 nomena such as sweating, lack of appetite, listlessness and disturbed 

 sleep and to fatal results if long continued (Lunin). Taylor (b) in a 9-day 

 experiment on himself during which he ingested a ration consisting of 70- 

 75 g. washed white of egg, 120 g. of fat and 200 g. sugar and containing 

 less than 0.1 g. of salts, per day, noticed especially the nervous symptoms 

 and a general muscular soreness. On the 9th day acetone was noticed in 

 the breath, and acetone and diacetic acid in the urine, whereupon the diet 

 was discontinued. The elimination of Ca and Mg through the urine ceased 

 entirely after four days ; Cl reached a minimum of 0.2 g. daily, phosphates 

 were constant and conjugated sulphates were abnormally high ; urinary 

 ammonia rose only on the appearance of diacetic acid, suggesting that the 

 fixed alkalies are required for the neutralization of the strong acids of S 

 and P. Urinary acidity was constant. Diuresis and a loss in body 

 weight (which was quickly regained on return to a normal diet) indicated 

 a loss of water from "the body. Goodall and Joslin repeated Taylor's experi- 

 mental procedure on two subjects, and in both cases failed to confirm the 

 appearance of either acetone or diacetic acid in the urine, although the 

 nervous symptoms were similar, and they agree with Taylor in finding 

 extremely low urinary chlorin, and considerable loss of weight due to a 

 loss of body water. Unfortunately no complete study of the mineral bal- 

 ance was made and the opportunity which these conditions gave for throw- 

 ing light on the fundamental mineral exchange in the body was lost. That 

 the undesirable symptoms are in part though not entirely due to the acid- 

 forming S and P present in the protein seems clear from the early work 

 of Lunin, who found that Na 2 CO 3 added to a salt-free diet prolonged 

 the life of mice to about double its duration without the Na 2 CO 3 but did 

 not prevent death with the usual symptoms. 



Fasting experiments have long been used to obtain fundamental infor- 

 mation upon the metabolism of organic matter. The excretion of inor- 

 ganic material during fasting gives similar information on mineral econo- 

 my. In the study of prolonged fasting made at the Nutrition Laboratory 

 of the Carnegie Institution ( Benedict (/O) it appeared that the excretion 

 of MgO (per kg. of body weight) was practically constant, especially after 

 the first six days, and was about one third of the Ca excretion. There was 

 a notable parallelism between the daily loss of Mg and of body protein 

 although the Mg was always slightly greater than the calculated value from 

 catabolized protein, using Magnus-Levy's figure of 0.106 per cent for the 

 Mg content of dry muscle. Sodium elimination gradually fell during the 

 first fifteen days, thereafter it was constant at a very low level (about 

 0.0011 g. Na per kg. body wt.) After the fifth day K 2 O formed ! 

 per cent of the total alkali excretion (Na and K). If muscle has three 

 times as much Mg as Ca and 5 or 6 times as much K as Na, mineral ehmi- 



