FEEDING EXPERIMENTS WITH ISOLATED FOOD SUBSTANCES. 9 



Lunin* on mice. Some of the animals were fed on casein as the sole 

 protein. They survived only a month or less on the "artificial" diet, 

 the author attributing the decline to defects in the intake of inorganic 

 salts and other accessory foods. 



Abderhalden and Ronaj fed mice with casein, sugar, and sodium 

 carbonate. The animals lived only 8 to 24 days on this obviously 

 inadequate diet. 



Falta and NoeggerathJ recorded the changes of weight in rats 

 kept on dietaries containing the nitrogen in the form of isolated 

 (commercial) proteins: ovalbumin, casein, serum albumin, serum 

 globulin, fibrin, and haemoglobin. They fed no "roughage" in the 

 form of cellulose. Neither these individual proteins nor mixtures of 

 all were adequate to keep the animals alive longer than 94 days in 

 the most favorable case. In most cases a gradual, steady decline was 

 noted throughout the progress of the experiment. Death occurred 

 when the animals had been reduced to two-thirds or three-fifths of 

 their initial weight. The experiments clearly demonstrate the neces- 

 sity of prolonged observation ; for rats were maintained on the casein 

 food mixture during several weeks without loss of weight, just as in 

 Henriques' briefer trials of three to four weeks. Only later did the 

 untoward effects manifest themselves. On milk, milk powder, or 

 lean horse-meat rats could be kept six months or more. 



The authors are properly guarded in their summary. They say : 



Ob in der Periode des Gewichtabfalles in unseren Versuchen die Tierc 

 gentigend Nahrung aufgenommen haben, um ihr Kalorienbediirfnis zu 

 decken, konnen wir nicht sicher angeben. Der Befund von Nahrungsresten 

 im Digestionstractus der toten Tiere (Lunin) ist unseres Eraehtens hierfiir 

 kein. zwingender Beweis. Hier miissten genaue Stoffweehselversuche mit 

 Berticksiehtigung der Kraftbilanz einsetzen. Erst wenn der Einwand 

 ungeniigender Nahrungsaufnahme oder ungeniigender Ausniitzung, fur 

 welehe beiden Momente man vielleieht die Einformigkeit der Kost und den 

 Mangel an Gewiirzen verantwortlieh maehen konnte, beseitigt ist waren 

 andere Griinde zu erortern, wie z.B. der Mangel der notigen chemischen 

 Bausteine oder ein abweiehendes ehemisches Gefiige der eingefiihrten 

 NahrstofTe. (p. 322.) 



Utilizing the experience gained in the preceding research, Knapp|| 

 succeeded no better in maintaining his animals. He estimates the 

 calorific needs of a 200 to 250 gram rat at 50 to 60 calories. The 

 curves of change of body-weight and caloric intake go more or less 

 parallel in Knapp's experiments and he notes that the specific role 

 of individual nutrients can not be suitably ascertained until animals 

 can be induced in some way to eat the requisite amount of calories 



*Lunin: Zeitschrift fur physiologische Chemie, 1881, v, p. 31. 



fAbderhalden and Rona: Zeitschrift fur physiologische Chemie, 1904, xlii, p. 528. 



JFalta and Noeggerath: Hofmeister's Beitrage zur chemischen Physiologie,. 1905, 



vii, p. 314. 

 ilKnapp: Zeitschrift fiir experimentelle Pathologie, 1908, v, p. 147. 



