224 THE BLOOD. 



existence of iron in it in combination with phosphoric acid ; 

 but it perhaps militates against this hypothesis when we 

 find that the white blood of the mollusca, although the con- 

 trary has been asserted, contains the same mineral ingre- 

 dients ; for Erman has detected iron, and very probably 

 also manganese, in the blood of the Helix pomatia and Pla- 

 norbis corneus ; and Poli likewise speaks of iron in the 

 blood of Area glycymeris. * As the following analysis 

 may probably be applied with safety to the whole class, I 

 extract the passage entire, notwithstanding it repeats some 

 particulars already noticed : " The blood of the He- 

 lix pomatia," says M. Gaspard, "is rather thick, but 

 without viscosity ; it has a faint smell, a slightly saline 

 taste, and is so abundant that each individual contains not 

 less than a drachm and a half. It is of a delicate blue 

 colour, which is neither altered nor modified by change 

 of aliment, by asphyxia, or by hybernation. It is mis- 

 cible with water, but of greater specific gravity, and falls 

 to the bottom in visible streaks or entire drops. When 

 exposed to the atmosphere it does not spontaneously con- 

 geal, like that of vertebrated animals, but it separates by 

 rest into two distinct fluids ; the one blue, which swims -at 

 the top ; the other colourless and opaque, remaining at the 

 bottom of the vessel. In a few days it decomposes with 

 fetor. It is unaltered by muriate of barytes and by alcohol ; 

 is simply discoloured by potash, and by vinegar and other 

 weak acids : but acetate of lead, nitrate of silver, and, still 

 more, nitrate of mercury, occasion a copious dense precipi- 

 tate. Boiling water, sulphuric and nitric acid, coagulate it 

 strongly, like albumen."^ 



* Rudolphi's Physiology by How, i. 113. 

 f Zool. Journal, i. 177. 



