89 



similar experiments with serum. The crystalline 

 lens forms the limit between the humours and 

 solid animal matter. It contains little more than 

 half its weight of water, and differs from other 

 secreted fluids in this, that it is less aqueous than 

 blood. It produces, when analysed, a portion of 

 acidulous extract, in which it resembles animal 

 matter, divested of its alkali. KEIL, had found, 

 that when the crystalline lens is treated with 

 dilute nitric acid, it is converted into a yellow 

 fibrous mass, like raw silk, its fibres diverging- from 

 the centre towards the surface, in a certain regu- 

 lar order. From this he concluded, that the lens 

 was a muscle, whose fibres were only rendered 

 visible by this treatment ; but, although the inte- 

 rior construction of the lens is as yet too little 

 known, to- enable us to explain the mechanism of 

 the phenomenon* still it is clear, from the solubi- 

 lity of the mass in water, and from its manner of 

 coagulation, that the lens cannot possess the pro- 

 perties of a muscle. 



The Tears have been examined by FOUR- 

 CROY and VAUQUELIN They resemble very 

 much the humours from serous membranes, and 

 the humours of the eye, but with this difference. 



