HISTORICAL SURVEY 25 



Hopkins were unknown, because he offered no experimental evidence 

 in their support till 1912. 2 



Till a short time ago, there was no lack of opinions which denied 

 the existence of substances essential to life. We have only to recall 

 the work of Abderhalden and Lampe in 1913 (25), although lately 

 Abderhalden has changed his view upon the matter. He (26) con- 

 ducted many feeding experiments with various proteins, hydrolyzed 

 meat, etc., without once recognizing that these diets were lacking in 

 something that was essential. 3 



It is true that the experiments did not last -very long, and that the 

 various constituents were not carefully purified. Incidentally, it 

 must be noted that in these experiments short periods, in which a 

 more natural diet was given, were frequently interspersed in order 

 to abate for a time the distressing deficiency symptoms. Above all 

 things, we must recognize that in dogs, the symptoms manifested 

 because of a deficient diet, are not so pronounced as in pigeons and 

 rats. Some time after the vitamine theory had already become 

 familiar, Abderhalden (29) found indeed that digested casein had less 

 value for growing animals than digested meat. He immediately 

 assumed that glycine was the cause of the difference, whereupon he 

 started various experiments, adding this amino acid, but naturally 

 without any success. Similar criticism may be made of the work of 



2 For instance, Rohmann (24) is mistaken when he asserts that the ideas 

 expressed by us originated with Hopkins. Inasmuch as we entered the field 

 in 1911, the statements of Hopkins were unknown to us. 



3 While I was working in the city hospital at Wiesbaden, I carried out under 

 Abderhalden's direction, some metabolism experiments with dogs. The 

 animals were fed with edestin, gliadin, milk powder and meat, together with 

 other usual dietary constituents. Since the experiments were considered 

 unsuccessful, only a small part of the work was published by Abderhalden 

 and my self (27). At that time, most of my dogs died, so that the feeding 

 experiments had to be started anew a number of times. Even then, I made 

 the observation that animals fed on edestin or gliadin quickly recovered on 

 addition of milk powder or meat. I wrote to Abderhalden a number of times, 

 that the edestin and gliadin combination was not sufficient to make the animals 

 thrive. The symptoms which I observed then recall those noted by Chit- 

 tenden and Underbill (28) in dogs fed on peas. To my letters, I received the 

 na'ive reply from Abderhalden, that in such metabolism experiments, success 

 depends upon the manner in which the animals are taken care of. I conscien- 

 tiously attempted to follow this advice, but the dogs, on such a poor diet, 

 refused to manifest any friendship for me. 



