80 SCIENCE PROGRESS 



nitrogen, but they actually retained a percentage of the nitrogen 

 given. An interesting fact was brought out in the course of 

 these observations as regards the calorific value of the de- 

 composition products. A calorimetric estimation of one gramme 

 of products was carried out by Rubner, with the result that 

 this amount was found to equal 4*599 cal., thus very similar 

 to the figure for albumen. There must be given, along with 

 these decomposition products, an abundant supply of carbo- 

 hydrate food in the form of sugar and starch. Recently 

 Luthje 1 has proved that it is absolutely essential that the 

 animal get carbohydrates, and further, that these carbohydrates 

 cannot be replaced by fat in the diet. The fact that Lesser, 2 

 who denied the correctness of Loewi's work, only used fat 

 and no carbohydrates, probably fully explains his negative 

 results. Loewi's results have been fully confirmed by other 

 workers, such as Henriques and Hansen, Abderhalden, and 

 others. Henriques and Hansen 3 not only were able to confirm 

 Loewi's results, but showed further that only a fraction of the 

 products produced by pancreatic digestion could keep the 

 animal alive. They found that those products which were 

 soluble in alcohol sufficed, whereas the insoluble fraction was 

 quite inert. Again, they showed that the part of the digest 

 not precipitated by phosphotungstic acid, that is the so-called 

 monamino acid fraction, had the nutritive value ; here, again, 

 the part precipitated was of no use as a food. This statement, 

 that a part merely of the products suffices as a food, has been 

 fully confirmed by Luthje (I.e.), always supposing, however, 

 that there be a plentiful supply of carbohydrate food in addition. 

 In this respect the animal body closely approximates the 

 vegetable kingdom, where it has been shown that carbohydrates 

 play a very important part in the protein synthesis. Abder- 

 halden 4 and his co-workers have also confirmed and extended 

 Loewi's results. As I have already mentioned, differences 

 were found between the nutritive values of protein digested 

 by trypsin alone and by pepsin followed by trypsin. They, 

 like Henriques and Hansen, found that although the products 

 arising from enzyme action were effective, those which were 



1 Luthje, Pfliiger's ArcAtv, 113, 1906, 547. 



2 Lesser, Zeit.f. Biol. 45, 1904, 497. 



3 Henriques and Hansen, Zeit.f.physiol. C/iem. 43, 1904, 417. 



4 Abderhalden and Rona, Zeit. f. physiol. Chem. 44, 1905, 198. 



