726 



SCIENCE 



[N. S. Vol. XXXIV. No. i 



failure may be; for ill health may be occa- 

 sioned by incidents quite apart from those 

 already outlined. Accident and acquired dis- 

 ease, unrecognized or uncontrollable, enter into 

 the life of every individual and serve to upset 

 an otherwise normal nutritive equilibrium. 



Turning to the present experiments, our 

 earlier attempts were largely based on those 

 of our predecessors. Comparative trials with 

 food mixtures precisely alike except for both 

 content and character of the inorganic in- 

 gredients soon showed the great importance of 

 this feature. A fairly suitable salt mixture 



was thus empirically selected. The table be- 

 low may serve to illustrate the character of the 

 earlier food mixtures which experience showed 

 to be most suitable. 



In such a mixture the protein can be varied 

 without serious change in the fuel value. 

 With one protein, viz., zein from maize, nu- 

 tritive decline was apparent from the outset. 

 The failure, as actual investigation showed, 

 can not be attributed solely to poor utilization. 

 With aU. the other proteins, such as casein, 

 legumin, edestin, glutenin or gliadin, in tha 

 mixtures indicated, grown rats have been 



Days" 

 Fig. 2. (Taken from Carnegie Publication No. 156, page 42.) This rat was fed for 169 days on 

 a, diet containing pure casein as the only protein. 



Per Cent, maintained in body weight for much longer 



Isolated protein 18 periods than we have found recorded by pre- 



Cane sugar 15 ^-^^g investigators. 



■ From many protocols we present three in 



■ ■ ■ 'j' _ graphic form ; the first to illustrate a failure 



„ „ . ^ „ _ from the outset, the second and third as ex- 

 Salt mixture ^-o 



amples of a relatively successful attempt over 



a period of 169 days and 259 days, respectively. 



" This indigestible carbohydrate was added to ^ every case-and we might cite very many 



furnish "roughage" in the diet. Cf. Mendel, such experiments under varied conditions— a 



Zentralblatt fur Staff wechsel, 1908, No. 17; decline ultimately ensued leading to death 



Swartz, "Nutrition Investigations on the Carbo- unless a dietary change was instituted. 



hydrates of Lichens, Algae, and Eelated Sub- It early seemed unlikely that the protein 



stances," Transatitions Connecticut Academy of was responsible for failures of this character; 



Arts and Sciences, 1911, XVI., pp. 247-382. for this foodstuff forms so large an essential 



