WILLIAMS : GLYCOGENIC FUNCTION IM THE MOLLUSCA. 35 



blood. In the MoUusca, Hammarsten^ has demonstrated that 

 in the Hver oi Helix pomatia it is present to the extent of 175 

 per cent., and that in hibernating animals of the same species, 

 and in the same organ, it is decreased to the amount of 0*429 

 per cent. Hoppe-Seyler has stated its existence in the liver 

 and muscles of the oyster ; D. Barfurth" has found it in 

 most of the tissues of Arioti, Limax, Helix and Cyclostoma, 

 while E. R. Blundstone'^ has discovered it in the mantle of 

 Anodon, and the mesentery of Helix. 



Whence comes this glycogen, and whither is it bound? 

 To answer these two questions we have to call to our mind 

 what is known of the physiology of the Vertebrates in this 

 connection, and compare it with what have been demonstrated 

 as existing in the Mollusca. There can be little doubt that 

 the mother-substance of glycogen in the Vertebrates, at any rate, 

 is carbohydrate food, while the ingestion of proteid matter 

 seems also to favour its production, but in a far less degree. 

 The former kind of foodstuff (starch) in them, is changed by 

 peculiar diastatic ferments — ptyalin of the saliva and amylopsin 

 of the pancreatic juice — into sugar which is taken up, as such, 

 from the enteric tract by the portal veins, and carried by them 

 to the liver, there to undergo by a process of dehydration its 

 conversion into glycogen. The latter is, in them, converted 

 into peptones by the action of the hydrochloric acid and 

 pepsin of the gastric juice, and the trypsin (in the presence 

 of sodium carbonate) of the pancreatic juice, and afterwards 

 split up in the liver into a non-nitrogenous portion (glycogen) 

 and a nitrogenous portion (probably urea). We have thus a 

 starch diet and an albuminous diet forming in the liver of the 

 Vertebrates a product — glycogen. Where does the analogy 



1. Arch. ges. Phys. xxvi. pp. 384-456. 



2. " Vergleichend-hestochemische Untersuchungen liber das Glycogen." 

 Arch. Mikr. Anat. xxv. pp. 259-404. 



3. " On the occurrence of Glycogen as a constituent of the Vesicular 

 Cells of the Connective Tissue of Molluscs." Proc. Roy. Soc. xxxvi. pp. 

 442-445 ; Abst. J. R. Micr. Soc. (2) v. p. 986. 



