THE MUTUAL RELATIONS. 



317 



mins to the carbohydrates. Clinical experience has long since decided 

 that albumin will produce sugar during diabetes. In no case, however, 

 is the proof clear and free from criticism. We are compelled to state 

 that at present we know nothing definite concerning the way sugar is 

 formed from albumin. It has been attempted to get around this problem 

 by placing especial stress upon the carbohydrate groups present in the 

 proteins. We have, however, already called attention to the fact that 

 the amount of carbohydrate groups present in proteins is of little quanti- 

 tative significance. To be sure, the carbohydrate content of the different 

 albumins from a practical standpoint will vary greatly, for we do not 

 feed animals with " pure " albumins, but albumin in the form of meat, 

 etc. Even then, however, if we were to assume that these albuminous 

 substances may contain as much as 10 per cent of carbohydrates, this 

 would not explain the appearance of the large amounts of sugar which are 

 eliminated by diabetics. E. Pfltiger himself has brought forward the best 

 proof in this direction, by feeding dogs with codfish, which is practically 

 free from glycogen and sugar. 1 This flesh contains 0.55 per cent fat. 

 The following table gives a summary of such an experiment: 



Here the case is perfectly clear. The question to decide is: Does the 

 eliminated sugar arise from fat or from albumin; i.e., to be more precise, 

 from the amino acids in the albumin? Only these two classes of food-stuffs 

 can be taken into consideration, and not the insignificant amount of carbo- 

 hydrate groups. The reverse process, the production of amino acids 

 from carbohydrates, undoubtedly takes place in plants. We have already 

 become acquainted with the close relations existing between glycerose (as 

 well as lactic acid, a derivative of the carbohydrates) and alanine, serine, 

 and cysteine, and have learned incidentally that the relations between the 

 other known albumin decomposition products to the carbohydrates still 

 remain unknown. The plant cells could hardly be considered as produc- 

 ing carbohydrates from albumin. Conversely, the animal cell unques- 



1 E. Pfluger: Pfltiger's Arch. 108, p. 136. 2 Cf. page 321. 



