314 LECTURE XIV. 



at the end of the test. Again, the methods employed in determining the 

 amount of glycogen were inaccurate in many cases. Finally, the experi- 

 menters have been satisfied, for the most part, with merely estimating 

 the amount of glycogen in the liver, entirely neglecting that which might 

 be retained in the other organs. This is on the assumption that the liver 

 is the place where the most glycogen is formed. We do not know, how- 

 ever, how the animal organism behaves when it has been deprived of its 

 carbohydrate stores. It is perfectly possible that the sugar will first go 

 to those organs which need it the most. The chief objection to all these 

 experiments is always that the ingested compound may have had an 

 indirect effect, i.e., when we add fat, to determine whether fat can produce 

 glycogen, and we do, as a matter of fact, find that this causes an increase 

 in glycogen, then the objection can be raised that perhaps the fat, which is 

 itself consumed, has acted as an albumin-sparer, so that the glycogen 

 may have been produced from albumin. The method of proof is, in every 

 case, an indirect one, and this makes it far more difficult to arrive at the 

 correct conclusion. In one arid the same experiment, the formation of 

 sugar may be traced back to either the fats or albumins, according to the 

 point of view. The same may be said of the second method of carrying 

 out the experiment. In this case, glucosuria is first produced, and then 

 the influence of various substances on the elimination of sugar is studied. 

 Thanks are due to E. Pfl tiger l for critically examining all of the investi- 

 gations which have been made up to the present time that have any 

 bearing on this subject, thereby showing with great clearness that the 

 whole problem is still in a very uncertain state. 



First of all, glycerol was tested with reference to its ability to produce 

 sugar; i.e., in other words, the problem was to decide whether the animal 

 cell is capable of synthesizing sugar from glycerol. This compound, as we 

 have already seen repeatedly, is related to sugar in its composition. We 

 have mentioned the hypothesis that glycerose is the starting-point in the 

 formation of glycerol by the plant cell, and in the same way we can regard 

 glycerose as resulting from glycerol when the plants convert fat into 

 sugar. Now the old idea that only the plant cells are capable of effecting 

 synthesis, has long since been set aside. We know that the animal organ- 

 ism is also able to build up. There is, therefore, no reason why sugar 

 could not be formed from glycerol. Of the many experiments which have 

 been performed in this direction, we will refer to those of Cremer 2 and 

 Liithje. 3 They fed dogs, whose pancreas had been removed, with glycerol, 

 and determined the increased elimination of sugar in the urine. Liithje 



1 E. F. W. Pfliiger: Das Glycogen u. s. Beziehungen z. Zuckerkrankheit, 2d ed. Bonn., 

 M. Eager, (1905). Cf. E. Pfliiger: Pfluger's Arch. 103, 1 (1904). 



J M. Cremer: Sitzber. Gesel. Morph. u. Physiol. Miinchen, May 27, 1902. 

 3 H. Luthje: Deut. Arch. klin. Med. 79, 498 (1904); 80, 101 (1905). 



