368 THE LIVER. 



The quantitative composition of the liver may show great varia- 

 tion, depending upon the kind and amount of the food supplied. The 

 amount of carbohydrate (glycogen) and fat may vary considerably, 

 which is due to the fact that the liver is a storage-organ for these bodies, 

 especially for the glycogen. 



Based upon special experiments, SEITZ l claims that the liver is a 

 storehouse for protein also. In experiments on hens and ducks which 

 had previously been starved, he found that the liver took up abundant 

 protein on feeding meat, and that its weight as compared with the weight 

 after starvation was doubled or quadrupled. As it is characteristic of 

 storage or reserve bodies that their amount in the storage-organs on 

 feeding with such bodies strongly increases in percentage, it is remarkable 

 in SEITZ' s feeding experiments that the percentage of protein in the liver 

 did not increase, but rather diminished slightly. In this case we did not 

 have a higher percentage of protein, but an increase in the weight of the 

 total cell mass of the organ, probably brought about by increased work 

 of the liver due to the protein feeding. It is also difficult to decide as to 

 how far in these experiments we are dealing with an increase in the 

 number or the size of the liver-cells or with a deposition of reserve 

 protein in the same sense as of glycogen or excessive fat. 



There is a unanimous belief that the liver is an especially important 

 storage-organ for glycogen. 



Glycogen and its Formation. 



Glycogen was first discovered by BERNARD. It is a carbohydrate 

 closely related to the starches or dextrinaf with the general formula 

 m(C6H 10 O 5 ). Its molecular weight is unknown, but seems to be very 

 large (GATIN-GRUZEWSKA and v. KNAFFL-LENZ 2 ) . The largest quan- 

 tities are found in the liver -of adult anima^ and smaller quantities in 

 the muscles (BERNARD, NASSE). It is found in very small quantities in' 

 nearly all tissues of the animal body. Its occurrence in lymphoid cells, 

 blood, and pus has been mentioned in a previous chapter, and it seems 

 to be a regular constituent of all cells capable of development. Glycogen 

 was first shown to exist in embryonic tissues by BERNARD and KUHNE, 

 (see also MENDEL and LEAVEN WORTH 3 ), and it seems on the whole to 

 be a constituent of tissues in which a rapid cell formation and cell 

 development are taking place. It is also present in rapidly forming 

 pathological tumors (HOPPE-SEYLER). Some animals, as certain mussels 



1 Pfluger's Arch., 111. 



2 Gatin-Gruzewska, Pfluger's Arch., 103; v. Knaffl-Lenz, Zeitschr. f. physiol. Chem., 

 46. 



3 Amer. Journ. of Physiol., 20. 



