I9I3] I' K. Phelps 85 



has shown that during digestion amino acids are absorbed into the 

 blood, as the amino-acid nitrogen of the latter, per 100 c.c, rises, in 

 a dog, from 4-5 mg. before feeding to 10—12 mg. after a meal of 

 meat. The low concentration of amino acids in the blood even at 

 its maximum indicates that the digestive products must be removed 

 rapidly from the circulation. This is found to be the case after 

 the injection of amino acids directly into the circulation. They dis- 

 appear from the blood almost as fast as they enter it. Analysis 

 of the tissues shows that these have absorbed the amino acids from 

 the blood, without subjecting them to any immediate chemical 

 change. This apparently follows later, but in the muscles the change 

 is so slow that no decrease in amino-acid nitrogen can be determined 

 within the first 3-4 hours after the injection. In the liver, on the 

 other band, the amino acids absorbed as the result of the injection 

 have entirely disappeared by this time, indicating that the metabol- 

 ism of these products is particularly rapid in the liver. It is less 

 so in the other organs, but whether as sluggish as in the muscles is 

 not yet certain. During starvation the amino nitrogen of the tis- 

 sues, which amounts to 40-80 mg. per 100 g. of fresh tissue, tends 

 to increase rather than disappear, indicating that the amino acids of 

 the tissues can originate from autolysis of the tissues themselves as 

 well as from digestion of food proteins. 



The configuration of some heptoses. George Peirce. 

 (Laboratory of Pharmacology and Toxicology, University of Wis- 

 consin.) J-a-Mannohexahydroxyheptoic acid and fl?-a-galahexa- 

 hydroxyheptoic acid yield, on oxidation, two pentahydroxypimelic 

 acids that are optical antipodes of each other. The configuration 

 of four of the asymmetric carbon atoms in each monobasic acid is 

 known and the configuration of the fifth is indicated by the above 

 fact. The corresponding heptites are also optical antipodes. Of 

 the four configurations on page 86, I and III are seen to be the two 

 that give optical antipodes on oxidation or reduction of the end 

 carbon atoms. These two are therefore the formulae for the a-com- 

 pounds. The /3-galactose Compounds of formula IV have been syn- 

 thesized but the /?-mannose Compounds of formula II have not yet 

 been prepared. 



