414 ANIMAL FOOD RESOURCES OF DIFFERENT NATIONS. 



report on oysters in 1876, especially praised the Portu- 

 guese oysters, which are obtained from about thirty miles 

 of coast extending from Lisbon to Cacillias Point. 



Dr. Fonssagrives, the learned author of "A Treatise 

 on Healthy Food," and Marine Surgeon-in-Ghief at 

 Brest, thus speaks of the oyster, and his remarks 

 within certain limits may probably be applied to other 

 moUusca: — 



" May we not suppose that these mollusks, living in 

 localities rich in iodine, collect this product and commu- 

 nicate it to those organisms which feed upon them, as in 

 the savoury products of Ostend and Concale. I am in 

 the practice myself of recommending oysters for weak 

 and lymphatic children with soft flesh, and making them 

 drink a sufficient quantity of the liquid given forth when 

 the oyster is opened, and I have found this exercise a 

 very favourable action." 



But there are other moUusca which may be said to 

 possess beneficial alimentary properties besides the 

 oyster. 



The oyster is almost the only animal substance which 

 we eat habitually, and by preference, in the raw or un- 

 cooked state ; and it is interesting to know that there is 

 a sound physiological reason at the bottom of this pre- 

 ference. Dr. Roberts, from whom we quote,* explains 

 this. The fawn-coloured mass which constitutes the 

 dainty of the oyster is its liver, and this is little else 

 than a heap of glycogen. Associated with the glycogen, 

 but withheld from actual contact with it during life, is 

 its appropriate digestive ferment — the hepatic diastase. 

 The mere crushing of the dainty between the teeth 

 brings these two bodies together, and the glycogen 

 is at once digested without other help by its own 

 diastase. 



The oyster in the uncooked state or merely warmed, 

 is in fact self-digestive. But the advantage of this pro- 

 vision is wholly lost by cooking ; for the heat employed 



* Lumleian Lectures before the Boyal College of Physicians. 



