TRANSACTIONS OF THE SECTIONS. Ill 



the attack of tetanus. He then asserted this amount of success to be 

 far greater than had ever been obtained, and that the uncomplicated 

 disease is no longer to be considered as either incurable or mysterious. 

 Dr. O'Beime concluded by stating that Mr. Walker, a veterinary sur- 

 geon of Dublin, to whom he had communicated his mode of treating 

 the disease in man, had succeeded in recovering seventy-three horses 

 affected vsdth tetanus. 



On the Cause, the Prevention, and the Cure of Cataract. By Sir D. 

 Brewster, F.R.S., 8;c. 



Having submitted to the Physical Section an account of a singular 

 change of structure produced by the action of distilled water u]"on the 

 crystalline lens after death. Sir D. Brewster was desirous of communi- 

 cating to the medical section some views which this, and previous 

 observations, have led him to entertain respecting the cause and the 

 prevention and cure of cataract. 



" The change of structure to which I have referred consists in the de- 

 velopment of a negative polarizing band or ring between the two posi- 

 tive rings nearest the centre of the lens ; the gradual encroachment of 

 this new structure upon the original polarizing structure of the lens ; 

 and the final bursting of the lens after it had swelled to almost a globu- 

 lar form by the absorption of distilled water. 



" As the crystalline lens floats in its capsule there can be no doubt 

 that it is nourished by the absorption of the water and albumen of the 

 aqueous humour, and that its healthy condition must depend on the 

 relative proportion of these ingredients. When the water is in excess 

 the lens will grow soft, and may even burst by its over absorption, and 

 when the supply of water is too scanty, the lens will, as it were, dry and 

 indurate, the fibres and laminae formerly in optical contact will sepa- 

 rate, and the light being reflected at their surfaces, the lens will neces- 

 sarily exhibit that white opacity which constitutes the common cataract. 



" This defect in the healthy secretion of the aqueous humour, as well 

 as the disposition of the lens to soften or to indurate by the excess or de- 

 fect of water, may occur at any period of life, and may arise from the 

 general state of health of the patient ; but it is most likely to occur be- 

 tween the ages of 40 and 60, when the lens is known to experience that 

 change in its condition which requires the use of spectacles. At this 

 period the eye requires to be carefully watched, and to be used with great 

 caution ; and if any symptoms appear of a separation of the fibres or 

 laminae, those means should be adopted which, by improving the general 

 health, are most likely to restore the aqueous humour to its usual state. 

 Nothing is more easy than to determine at any time the sound state of 

 the crystalline lens ; and by the examination of a small luminous image 

 placed at a distance, and the interposition of minute apertures £uid 

 minute opake bodies of a spherical form, it is easy to ascertain the exact 

 point of the crystalline where the fibres and laminae have begun to sepa- 

 rate, and to obsen'e from day to day whether the disease is gaining 

 ground or disappearing. 



