38 WILLIAMS : GLYCOGENIC FUNCTION IN THE MOLLUSCA. 



in the tissues in some kind, if not in the form of glycogen, for 

 the wants of the system during hibernation, and also to supply 

 energy by oxidation, during prolonged muscle-contraction since 

 Simroth^- has stated that a small Helix can move along when 

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

 note communicated to the tenth volume of " The Zoologist " 

 (p. 491) entitled "Experiments to Test the Strength of Snails " 

 has proved that a Helix aspersa weighing one-third of an ounce 

 can draw along an horizontal plane a weight weighing seventeen 

 ounces, and that another of the same species of 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; while 

 according to the researches of F. Plateau^ ^ the absolute force — 

 /. e. the weight which a muscle stimulated to the utmost is just 

 able to raise — estimated on one square centimetre of the mean 

 transverse section is nearly equal, with their unstriated muscle- 

 cells that differ so slightly from the ordinary type of protoplasm — 

 is nearly equal to that estimated for the Vertebrates with their 

 more differentiated striped muscle-fibres. The largest estimates 

 made by this observer on the adductor muscles were for Venus 

 verrucosa (12,431 grammes), Pectimculus glycy uteris (10,152 

 grammes), and Mytilus edidis (7,984 grammes ; the lowest for 

 Pecten opercularis {^2>° gx2.mxi\Q.'^). For comparison's sake, the 

 absolute force of a frog's muscle is 2*8 to 3 kilogrammeters ; 

 of human muscle, 8 to 9 kilogrammeters. The great drawbacks 

 to our future knowledge of the physiology of the MoUusca are 

 the evident ones of the difficulties attending the performance of 

 minute experiments on account of the small size of their organs 

 and the incapability of keeping them alive for a sufficiently 

 lengthened period under the influence of proper anaesthetic 

 conditions. The consideration occurs to the author that it is 



12. "Die Thatigheit der willkurlichen Miiskulatur unserer Land- 

 schnecken " Z. wiss. Zool. xxx. suppl. vol. pp. 166-224. 



13. " Recherches sur la force absolue des muscles des Invertebres." 

 I. Partie. Bull. Ac. Belg. (3) vi., pp. 226-259. 



J.C., vi., Jan., 1889. 



