320 LECTURE XIV. 



immediately determined the amount of glycogen in one of these, while 

 the remainder were cultivated upon the albumin from hens' eggs. He 

 could not observe any formation of glycogen in this case, although positive 

 results were obtained when the maggots were nourished with meat. These 

 experiments do not furnish a direct proof that sugar is formed from albu- 

 min. We know now that neither the albumin from hens' eggs nor from 

 meat is free from sugar. It is possible that the glycogen produced by the 

 maggots results from the sugar in the food. Numerous feeding experi- 

 ments with animals fed exclusively on albumin in the form of meat, etc., 

 have, without exception, led to the conclusion that glycogen is produced 

 from albumin. 1 It would take too long to dwell upon all of these experi- 

 ments. Many of them can be thrown out because there was sufficient car- 

 bohydrate present in the food to account for the glycogen found. On 

 the other hand, in many cases it was not shown that the animals under- 

 going experiment contained no glycogen at the beginning of the test. 

 Finally, we must add that improvements in the methods of estimating 

 glycogen have shown the unreliability of values formerly obtained. Thus, 

 8.5 grams of glycogen was assumed as an average content per kilogram 

 weight of a dog. Pfliiger increased this value to 11 grams, while to-day 

 we regard 41 grams as more nearly correct. 



It will be sufficient if we compare the two series of experiments of 

 E. Pfltiger and H. Liithje, 2 which are free from criticism. We have already 

 given Pfliiger's figures, and will add merely that he in one experiment, 

 for example, found the following balance: 



Total sugar formed '. 3097.1 grams 



Explainable as residual glycogen 422 . 3 grams 



Sugar formed from other sources 2674 . 8 grams 



This result corresponds with that of Liithje, and proves positively that 

 sugar must have been formed from some other source than carbohydrates. 

 Liithje also fed casein to a dog whose pancreas had been removed. The 

 animal weighed 5.8 kilograms. It eliminated 1176.7 grams of sugar 

 between October 2 and November 24. E. Pfliiger 3 subtracts 650.6 grams 

 from this as being due to sugar present in the food and from the glycogen 

 originally present in the body. It must be said that this value subtracted 

 by Pfliiger is, if anything, too high rather than too low. 4 Thus, at least, 



1 Cf. E. Pfliiger: Glycogen, loc. cit. p. 240, etc. 



2 H. Liithje: loc. cit. Deut. Arch. klin. Med. 79, 4999 (1904). Pfliiger's Arch. 106, 

 160 (1904). 



3 E. Pfliiger: Pfliiger's Arch. 106, 168 (1904). 



4 E. Pfliiger calculates 109 grams sugar from 328 grams of serum-albumin, basing 

 this on the values obtained from mucin by F. Miiller. Serum-albumin and serum- 

 globulin contain, at the most, 2 per cent sugar. If we take out 7 grams sugar as due 

 to the serum-albumin, we would undoubtedly be placing the sugar value too high 

 rather than too low. Liithje administered 4100 cubic centimeters serum. Since 1000 



