1865.] Mr. Foster on Glycogen in Entozoa. 545 



that there is no sugar-forming ferment present in the tissues of the Ascaris. 

 Portions of the tissues may be kept exposed to a temperature of 35 C. for 

 many hours without any appreciable loss of glycogen or advent of sugar. 

 The whole animal, too, may be kept for days without any change of its 

 glycogen being observed. I also failed to extract from the tissues any 

 ferment capable of acting upon starch. The intestine alone seemed to 

 have any power of the kind, and that but in the very feeblest degree. This 

 failure in the production of sugar is not due to the presence of any sub- 

 stance antagonistic to the action of a sugar-forming ferment ; for the addi- 

 tion of a small quantity of saliva to even the unboiled tissues very speedily 

 brings about the conversion of the glycogen into sugar. "We may infer 

 therefore that, if the animal swallows the intestinal juices in which it lives, 

 the sugar-forming ferment contained therein either does not pass through 

 its intestinal wall into the visceral cavity, or, if it does pass, is at once de- 

 stroyed. It is evident that the formation of glycogen in the Ascaris takes 

 place under conditions very different from those under which glycogen is 

 deposited in the mammalian liver, since in the latter case there is present 

 a powerful sugar-forming ferment belonging, as we have reason to believe, 

 to the liver-substance itself, and not merely to the blood passing through 

 the organ. 



The possible use of this glycogen is a matter of interest. Intestinal 

 worms, inasmuch as they are animals and live, must needs consume oxygen. 

 The amount of that gas they find in the intestinal juices, however, is very 

 small; and, having a constant temperature secured to them by warmth 

 external to themselves, they are the very last of creatures to need what 

 has been called " respiratory or calorifacient material." Whatever be the 

 use of sugar, starch, or glycogen in the mammalian body, no " respiratory" 

 use can be safely suggested for the large amount of glycogen occurring in 

 the Ascaris. Its abundance in the muscular parietes might suggest that 

 it was material on its way to become muscle. If so, since the animals I 

 studied were adults and ova-producing, the analogy of their glycogen would 

 be, not with the glycogen of the muscles of the early mammalian embryo, 

 but with the glycogen (or dextrine) occurring in smaller quantities in the 

 full-grown muscles (unless one were to push an idea, and say that the 

 tissues of the lower animals were chemically homologous with the em- 

 bryonic tissues of the higher ones) . 



It might be thought to be immature chitin ; but why should it exist in 

 such quantities? and why is there so little in the caterpillar and the 

 maggot ? In the Tsenia the glycogen could hardly be thought to have a 

 muscular future. There it might be considered to be stored up for the 

 development of the ova. This idea is at first sight contradicted, as far as 

 the Ascaris is concerned, by the fact that very little glycogen can be ob- 

 tained from the generative apparatus of that animal. But is it not pos- 

 sible that, though stored up elsewhere, it may really be intended for the 

 ova and embryos after all ? The analogy between the Ascaris, with its 



