EFFECTS OF INANITION ON THE BODY AS A WHOLE IOI 



as inorganic salts and the recently discovered vitamins, so that they often repre- 

 sent mixed deficiencies of uncertain character from which no definite conclusions 

 can be drawn. In the second place, only within the past decade has it been 

 generally recognized that the quality of the dietary protein is even more impor- 

 tant than the quantity (Hart, McCollum, Steenbock and Humphrey 'n). 

 Chiefly through the investigations of Osborne and Mendel ('n, 'ua, '12a, 

 '12b, '14, '15, '15a, '16b, etc.) and their co-workers it is now recognized that 

 among about 18 amino-acids which, in varying proportions, constitute the ordi- 

 nary proteins of foods, several, though essential for nutrition, cannot be synthe- 

 sized in the animal body and must therefore be present in adequate amount in 

 the food-intake. Among these essential amino-acids, tryptophan, lysin, tyrosin, 

 and cystin are especially important for normal growth, which is prevented or 

 retarded in the absence or insufficiency of any one of them. Liebig's "law of 

 the minimum" is therefore considered applicable to the essential amino-acids 

 in the diet (Osborne and Mendel '15a, '16b). Thus on account of their varying 

 amino-acid content, diets with some isolated proteins (gliadin, edestin, glutenin, 

 casein) may permit maintenance of young rats without growth for long periods, 

 while others (zein, gelatin) do not even suffice for maintenance, but occasion 

 more or less rapid decline in body weight. 



Contrary to the previously mentioned results of (incomplete) total inanition 

 in man and animals, Osborne- and Mendel ('n, 'ua), in young rats held at 

 maintenance for long periods (up to a year or more) by incomplete protein diets, 

 found no changes in the body proportions, excepting the possibility of continued 

 growth in the nervous system. Mendel and Judson ('16), however, described 

 persistent skeletal growth in mice retarded by diets inadequate in protein or 

 salts, as well as by simple underfeeding. Mendel later ('17) described abnor- 

 malities of growth on various insufficient or inadequate diets. 



Recovery upon Refeeding. — Osborne and Mendel also ('n, 'na, '12a, 

 '12b, '14a, '15a; Mendel '14, '15) found in the retarded rats a remarkable capacity 

 for recuperation upon adequate refeeding, and concluded that it seems impos- 

 sible by this type of inanition, no matter how long continued, to suppress the 

 capacity for growth, or to produce permanently dwarfed individuals. It also 

 appears possible in this way to increase the total span of life in rats, and refed 

 females have borne apparently vigorous young after the normal age of meno- 

 pause (Osborne and Mendel '17). Wheeler ('13) likewise obtained normal 

 recovery in young mice retarded in growth for long periods on gliadin or casein 

 diets. 



This failure to produce permanent dwarfing by long continued suppression 

 of growth in rats and mice on incomplete protein diets is in striking contrast 

 with the (previously mentioned) results of Jackson and Stewart and others 

 in animals dwarfed by underfeeding. It should be noted, however, that the 

 incomplete protein experiments were not begun upon very young animals, 

 and it is possible that a similar retardation of growth at earlier stages (between 

 birth and the weaning period) would result in permanent dwarfing, as found in 

 rats by the underfeeding experiments, and in certain types of partial inanition 

 (to be mentioned later). 



