ANATOMY AND PHYSIOLOGY OF A SNAIL. 31 



that the mother-substance of glycogen in the Mollusca is the same 

 as that in the Vertebrata. What its destination in the Mollusca 

 may be, we have very little direct evidence to guide us to a safe 

 conclusion. In the Vertebrates, it is no doubt devoted to the 

 production of heat and muscle- energy. Broken up, in them, by 

 a blood-ferment again into sugar, as the exigencies of the system 

 demand, it is taken by the radicles of the hepatic vein to undergo 

 katabolic changes in the tissues. And that it is used up during 

 muscular contraction by them does not admit of a doubt, for it 

 has been experimentally proved that all the glycogen disappears 

 during movement. What about the Mollusca? Barfurth has 

 demonstrated that the quantity present in the muscles of Helix 

 is inversely proportional to their activity, and should Wooldridge's 

 theory that the Vertebrate blood-ferment is lecithin prove to be 

 a fact, we have here two things that unite together to show, 

 disregarding the facts we have already mentioned, that glycogeny 

 in the Mollusca and in the Vertebrata are far from being dissimilar, 

 since lecithin is present in the Molluscan blood. But, whatever 

 its destination in the Mollusca may be, it is a point well worthy 

 of mention in connection with this, that a large amount of reserve 

 material must be stored away in their tissues in some kind, if not 

 in the form of glycogen, for the exigencies of the system during 

 hibernation, and also for prolonged muscular contraction, since 

 Simroth has stated that a small Helix can move along when 

 burdened with a weight nine times its own, and Sandford has 

 proved that a Helix aspersa^ weighing one-third of an ounce, can 

 draw along a horizontal plane a weight weighing seventeen 

 ounces (fifty-one times its own weight), and that another of the 

 same species, one-quarter of an ounce in weight, can drag a weight 

 of two and a quarter ounces after it when moving along a vertical 

 plane (nine times its own weight). 



Glycogen is rather a difficult substance to prepare pure, but 

 the steps of the process are as follows. The organ suspected to 

 contain it is taken from a recently killed animal, cut up into 

 pieces, and plunged into boiling water in order to destroy any 

 ferment that may be present, then boiled for some time and 

 filtered. The filtrate is allowed to get cool, and dilute hydro- 

 chloric acid and potassio-mercuric iodide are alternately added to 



