HISTORICAL SURVEY 21 



mice cannot maintain themselves on a diet composed of bread, and 

 milk which has been extracted with alcohol. If, however, the 

 extracted portion is recombined with the diet, then the animals 

 begin to grow once more. In another communication, Stepp (7) 

 was convinced that his findings were not due to the loss of salts 

 during extraction, and classified in the lipoid group, those substances 

 essential to life. In spite of the fact that this conclusion was not 

 quite justified, the work of Stepp really merited more attention than 

 it received at the tune of its publication. Unfortunately, this was 

 not the case, for the relegation of the substances necessary for life 

 to the class of lipoids, which already had been considered essential, 

 did not signify real progress. 



Aside from the work of Stepp, attention could easily have been 

 focused upon the conception of the vitamines by research which had 

 for its purpose the study of the importance of salts in nutrition. 

 Relative to this, the school of Bunge is credited with a great deal of 

 merit. Another series of investigations dealt with the utilization of 

 purified foodstuffs, especially in the mouse, the rat and the dog. 



In 1873, Forster (8) tried to determine whether or not dogs could 

 maintain themselves on an ash-free diet. For this purpose, he fed 

 the meat remaining after the preparation of Liebig's meat extract. 

 These residues were washed repeatedly with distilled water until 

 they contained only 0.8 per cent ash. They were then combined 

 with fat, sugar and starch, and fed to dogs, with the result that they 

 died sooner than starving animals. Experiments with pigeons, fed 

 with casein and starch (and occasionally a little fat), gave the same 

 results. The symptoms noted by Forster, in pigeons, were partic- 

 ularly interesting. They refused food, lost a great deal of weight, 

 showed weakness, opisthotonos and characteristic circular motions. 

 As we shall see later, these symptoms, which Forster attributed to a 

 lack of salts, were apparently identical with "poly neuritis galli- 

 narum," a disease of chickens described by Eijkman in 1897. This 

 view is further strengthened when we note the length of time that 

 the pigeons lived 13, 26 and 31 days. In dogs, there was noted 

 tremor, peculiar gait and weakness similar to that of paresis. 



The investigations from Bunge's laboratory, which are mentioned 

 in his book on physiological and pathological chemistry (9), are 

 worthy of attention. Lunin (10) reported experiments with mice, 

 fed on casein, fat and cane sugar. Out of five animals used, one 



