46 LECTURE III. 



molecule can take place, as with starch, step by step, and quite anal- 

 ogous products are obtained here. Diastatic ferments likewise attack 

 glycogen. Among the decomposition products obtained by hydrolysis, 

 dextrin and maltose have been identified with certainty. In its other 

 relations it is exactly similar to starch, and here as in the case of the 

 compounds of higher molecular weight formed from it (the dextrins, for 

 example) , we have no guarantee concerning their individuality, and sim- 

 ilarly we do not really know whether glycogen itself is a simple com- 

 pound or a mixture. 



We do not yet know with sufficient certainty whether glycogen as such 

 is deposited in the tissues, or whether at least a part of it may not be 

 present in a combined state. 



Glycogen is widely distributed in the animal kingdom, and is found in 

 all sorts of different tissues. 1 One of its chief sources is the liver, in which 

 it is deposited in the cell-substance. The nucleus is always free from it. 

 The amount present depends greatly upon the condition of nourishment 

 of the animal. The liver contains this polysaccharide even in its early 

 stages of development, 2 although perhaps in small amounts. It is also 

 found in organs corresponding to the liver in many invertebrates, thus, in 

 crabs, mollusks, etc. 



Detailed studies have been made concerning the distribution of glycogen 

 in the liver of the Gasteropoda. It was found that the content of glycogen 

 was dependent upon precisely the same conditions as with Vertebrata. 

 In the case of Limax and Helix the entire glycogen content could be made 

 disappear at the end of twenty to twenty-one days. After feeding, it 

 reappeared in the course of nine or ten hours. It is first deposited in the 

 connective tissue, and then in the epithelium of the liver. Starvation 

 alone causes it to disappear. With the gasteropods the liver is the only 

 place in which glycogen is deposited to any extent; in the other organs 

 the amount is hardly worthy of consideration. 



Also in the lower organisms, other than mollusks and gasteropods, 

 glycogen is widely distributed. Bernard found it in the larvaB of flies, 

 the grubs of many insects, in earth-worms and tape- worms, etc. Other 

 authors have mentioned its occurrence in Echinoderms, Holothuria, 

 Polyps, Sponges, etc. 



Glycogen has likewise been identified in Protozoa (Vorticella, Opalina, 



1 For the microchemical detection of glycogen, see Dietrich Barfurth: "Verglei- 

 chende histochemische Untersuchungen liber das Glykogen," Arch, mikro. Anat. 26, 

 259 (1895), and Edgar Gierke: "Das Glykogen in der Morphologic des Zellstoffwechsels," 

 Habilib-Schrift, G. Fischer, Jena, 1905. 



2 E. Pfliiger: Ueber den Glykogenhalt der fotalen Leber, Pfliiger's Arch. 96, 19 

 (1901), and Glykogengehalt der fotalen Leber und die Jodreaktion des Glykogens," 

 ibid. 102, 305 (1904). 



