28 Hugh Davson 



continuously redistributing themselves so that the osmotic 

 pressure of this phase is greater than that of extracellular 

 fluid and of blood. The extent to which the system will 

 take up water will depend on the counter-pressure that can 

 be exerted or, failing that, what is really equivalent, the 

 mechanical rigidity of the system that will oppose distention. 

 Presumably in such tissues as tendon and skin the structural 

 rigidity of the system prevents an indefinite uptake of water, 

 and the system is stabilized with a water content of about 

 75 per cent. In the cornea of the eye, however, the situation 



is different; it consists, essentially, of a number of laminae of 

 collagen-plus-mucoid, sandwiched between two cellular layers, 

 the epithelium and endothelium. If the eye is excised and 

 stored in the cold, say at 4°, the cornea increases in water 

 content, due to absorption of aqueous humour. If instead of 

 being kept at 4° the eye is maintained at about 31° — the 

 normal temperature of the cornea — the tissue retains its 

 normal water content (Table III). It would seem, then, that 

 metabolic activity is preventing the collagen plus mucoid 

 from absorbing water and salts from the aqueous humour, and 

 this may be proved by first allowing the cornea to swell at the 



