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 
Liithje! 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,? 
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? 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 Liithje (/c.), 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‘ 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 Liithje, Pfiger’s Archiv, 113, 1906, 547. 
2 Lesser, Zezt. f. Biol. 45, 1904, 497. 
3 Henriques and Hansen, Ze7t. f. Physiol. Chem. 43, 1904, 417. 
4 Abderhalden and Rona, Zezt. f. physiol. Chem. 44, 1905, 198. 
