ARTERIES AND VEINS. 421 



Lassaigric analysed an opaque lens from a horse. It con- 

 tained : 



Coagulated albumen . . . 29-3 



Phosphate of lime . . .57*4 



Carbonate of lime . . .1*6 



Soluble salts and other matters . .177 



The vitreous humour is perfectly clear and contains a very 

 small amount of solid constituents in solution. It is enclosed 

 in numerous compartments by a very delicate transparent mem- 

 brane. On removing it by gentle pressure from this membrane, 

 and evaporating it to dryness, it yields only -0162 o f a colourless 

 residue consisting for the most part of chloride of sodium. 

 Berzelius obtained from it : 



Water . . . . . 98-40 



Albumen . . . . .0-16 



Chloride of sodium with a little extractive matter . 1*42 



A substance soluble in water . . . 0-02 



The aqueous humour contains, according to Berzelius : 



Water ..... 98-10 

 Albumen . . , . .a mere trace 



Chloride of sodium with a little alcohol-extract . 1-15 

 Extractive matter soluble only in water . . 0-75 



The Arteries and Veins. 



Very little is known with certainty regarding the chemical 

 composition of the different coats of the blood-vessels, but their 

 microscopic characters have been thoroughly examined by Henle. 

 Berzelius has shown that the middle coat of the arteries belongs 

 to the elastic tissues ; Eulenberg, on the other hand, asserts that 

 from 30 grains of dried arterial membrane (middle coat) he ob- 

 tained, by three successive boilings, occupying in all 120 hours, 

 1 1 grains of dried substance which dissolved in water and gela- 

 tinized on cooling. Valentin found that an acetic-acid solution of 

 arterial membrane is precipitated by ferrocyanide of potassium, 

 and I have obtained a solution of the middle coat (by boiling it 

 in water for ten hours) which is strongly precipitable by acetic 

 acid. The greater part of the precipitate dissolves in an excess 

 of the acid, and is again thrown down by ferrocyanide of potas- 



