386 Chemical Properties of Animal Fluids. [Nov. 



of the eye are not coagulated by boiling. Their composition is 

 as follows: — 



Aqueous Humor. Vitreous Humor. 



Water 9S-10 98-40 



Albumen a trace 0-16 



Muriates and lactates 1*15 1*42 



Soda, with animal matter? 0<) -- . .-, 



soluble only in water ... 5 



The crystalline lens has a peculiar and very remarkable com- 

 position. It has been considered as a muscle from the well- 

 known experiment of M. Reil, who, on treating it with nitric 

 acid, discovered in it a peculiar muscular structure ; and Mr. 

 Clicnevix also found that its density and specific gravity increased 

 towards the center. But its solubility in water is a sufficient 

 proof that it is not a muscle, though to effect this solution it is 

 necessary to break it down, and then it leaves undissolved a small 

 portion of extremely pellucid membrane. This circumstance, 

 added to that of the increasing density towards its center, shows 

 that the structure of the lens is cellular, the cells being filled 

 with pellucid matter of different degrees of concentration. 

 The composition of the lens I have found to be as follows : — 



Water 58-0 



Peculiar matter 35*9 



Muriates, lactates, and animal matter, all"? 



soluble in alcohol 5 



Animal matter soluble only in water, with? _ 



some phosphates 5 



Portions of the remaining insoluble cellular? „ . 



membrane 5 



100-0 



The matter peculiar to the lens is remarkable. It coagulates 

 by boiling, and the coagulum has all the chemical properties of 

 the colouring matter of blood, except colour, which is entirely 

 absent. When burnt, it leaves a little ash, containing a very 

 small portion of iron. The liquor in which the coagulum is 

 formed reddens litmus, has the smell of the humors of the 

 muscles, and like them contains free lactic acid. 



The perfect achromatic- transparence of the lens, notwith- 

 standing its similarity in chemical properties to the colouring 

 matter of the blood, is well worthy of notice. The black pig- 

 ment of the choroidea is a powder insoluble in water and acids, 

 but slightly soluble in alkalies. When dried and ignited, it 

 burns as easily as a vegetable substance, and the ash contains 

 much iron. From these observations it may well be supposed 



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