ZOOLOGY. 355 



in various stages. The condition was temporary, and would pass 

 away slowly as the agent producing it left the system of the animal. 

 Different substances produced different characters of the cataract: 

 thus, cataract produced by salines was harder than that produced 

 by sugar. All the soluble blood-salts present in the blood in excess, 

 produced the same condition. Having thus described the produc- 

 tion of cataract, Dr. Richardson showed its connection with disease 

 by the fact that diabetes a disorder in which sugar is present 

 in excess in the blood is attended in one in every four cases by 

 cataract more or less developed ; and it is probable, although not as 

 yet demonstrated, that there were other diseased conditions in which 

 saline constituents by excess induced the same condition in the 

 human subject. 



The last point to be considered was, why does the crystalline lens 

 undergo opacity ? Many years ago, Sir David Brewster, at a meet- 

 ing of the Association, had pointed out that the opacity of the crys- 

 talline lens in cataract depended upon disarrangement of the fibres 

 of the lens ; but the reason of the disarrangement had not been ex- 

 plained, neither had Sir David's view, though quite correct, been 

 generally accepted. The experiments conducted by Dr. Mitchell 

 and the author proved that the opacity, which ordinarily commences 

 in the back part of the lens, is due to an irregular clustering together 

 of the fibres, and to external softening. This change is brought 

 about by osmosis, or transference of water from one body to another. 

 He, the author, as well as Dr. Mitchell, had, in his earliest inquiries, 

 arrived at this conclusion ; but the nature of the osmotic act was now 

 more fully developed by the recent researches of Dr. Graham on 

 liquid diffusion. Dr. Graham had divided all bodies into two great 

 classes, the colloids and the crystalloids. The former, represented by 

 gelatine, are constantly undergoing change and yielding up their 

 water ; the latter receive and fix water : hence, in contact, in water, 

 the crystalloids will become universally distributed, while the colloids 

 will separate. The crystalline lens is a true colloid, containing in 

 health a certain given portion of water, upon the presence of which 

 its transparency depends. But whenever there is such a deviation 

 in the blood, in the amount of crystalloid, that that amount is in- 

 creased, the colloid structures undergo a derangement, owing to an 

 abstraction of the water which they contain. This is what occurs to 

 the lens in cataract, a disease which becomes, by this explanation, a 

 physical phenomenon of the simplest class. 



RESUSCITATION. 



The following interesting paper was read before the British Asso- 

 ciation (1861) by Dr. Richardson: 



It has been conceived by many of the eminent physicians of past 

 times that a day would come when a knowledge of life would be so 

 far advanced that, after certain forms of death in which the organic 

 structures of the body were not injured, such as deaths by suffoca- 

 tion, by some poisons, by shock, and the like, it would be possible to 

 produce re-animation. This, which was formerly but an idea, is 

 now, by the course of physiological research, almost a reality. Death, 



