NUNNELEY, ON THE CRYSTALLINE LENS. 145 
This he calls crystalline. He gives the composition of the 
lens. 
In the ox. In the horse. 
Water ‘ - : » 165°762 60-000 
Albumen : : , « ,28:290 25°531 
Crystalline , : : - 10°480 14-200 
1 eK Te f ss : . 0:045 0°142 
Extractive matter, with chloride of sodium and 
lactates . ; f - 0495 0:426 
That the lens consists of fibres arranged side by side, in 
concentric layers, superimposed upon each other, com- 
mencing at the axis and passing from one surface or pole to 
the other, has long been known, particularly through the 
labours of Leeuwenhock, Derham, and Dr. Young; and that 
the human lens has a tendency to split at first into three 
sections, and then again into smaller, ordinary decomposition 
or immersion in weak spirit, boiling water, and other coagu- 
lating agents, readily shows; but the exact nature and 
arrangement of these fibres were much debated and disputed 
until a recent date. We are indebted to Sir D. Brewster for 
the first accurate account of the microscopic anatomy of 
this body,* and though in all particulars his description may 
not be fully borne out, yet his investigations did much to 
reveal the wonderful complicity of the minute anatomy of 
the lens. 
In order to examine the lens microscopically it should be 
rendered opaque, and hardened by alcohol, chromic acid, or 
hot water. If boiled for any length of time the fibres be- 
come irregular. I find immersing the lens for three or four 
minutes in water at 160°, and then adding to the morsel on 
the object-glass a drop of very dilute chromic acid, to 
develope the structure well. Acetic acid renders the fibres 
beautifully transparent and clear, but does not harden them 
so much as chromic, and soon acts upon them destructively. 
Liq. potassz destroys them immediately, ammonia more 
slowly. 
The lens of a large fish, the cod or haddock for instance, 
or of the frog or toad, should be selected for first observa- 
tions, as the fibres are stronger and their markings coarser 
than they are in birds, mammalia, or man; and of these 
lenses the middle portion should be selected, as upon the 
outer surface or margin the fibrous character is not well 
developed, and near the axis the fibres are so attenuated and 
delicate that their serrations are not so distinct. In other 
respects, in all orders of animals, the fibres appear to be 
* ¢Phil. Trans., for 1833 and 1836. 
