Here, then, we find that common salt administered to the lower animals, causes a development of cataract in them.
In his experiments Kunde was aided and controlled by Kolliker, Virchow, H. Muller and Von Graefe. His experiments have been repeated by Kohnhorn, in Germany, by Weir Mitchell in America, and by B.W. Richardson, in England, and amply confirmed.
I hope you will pardon my going over the ground so well known to you all, but I want to bring out very prominently this importance fact, that the common salt of our tables is a ready producer of cataract.
In my little treatise “Supersalinity of the Blood,” etc., I take up this idea, and endeavour to show that not a few of the cases of cataract that come before us, have their origin in the excessive use of salt.
When too much salt is ingested, the blood becomes supersaline; when the blood is supersaline, its specific gravity is raised, and the lens is deprived of its natural condition as a transparent body,-in fact, it becomes opaque. If this condition of the blood continue for any lengthened period the lens must necessarily degenerate, and the cataractous state becomes permanent. I have shown that very many cataractous patients are fond of salt, and I submit that the salt must, in not a few instances, be held responsible for the dried up, sclerosed state of the lens and other tissues of the body.
The physiological effect of salt upon our bodies is to dry up, to deprive of water, to harden, and hence salt makes us thirsty. This is, I hold, with Kunde, the essentiality of its action, Weir Mitchell and Richardson to the contrary notwithstanding.
Let us now pass on to the next cause of cataract, viz., to
The Use of Sugar as a Cause of Cataract.
The experiments of Weir Mitchell, as set forth in a paper in the American Journal of the Medical Sciences, for January, 1860, show that not only salt, but also sugar can cause cataract. I have not read this paper myself, but only know it from Richardson’s references to it. Hence I must refer to the experiments of Richardson that were undertaken to the same end, and gave a like result, i.e., sugar causes an opacity of the crystalline lens.
When a patient comes to you, and you find the lenses opaque, the skin dry, the quantity of urine excreted large, the thirst great, and the specific gravity of the urine much increased-say 1040 or 1045-then you test the urine, and find it is full of sugar, you say your patient has diabetic cataract.
Ophthalmologists were well acquainted with this clinically, long before science showed that saccharine cataract could be synthetically produced. I believe the honor of this discovery belongs to America. But science knows no territorial frontiers and no nation, and her fruits belong to mankind.
Although it has been so long known that the diabetics are apt to get cataract, and although it is more than twenty years since Mitchell showed that cataract can be induced in the lower animals by putting sugar into their bodies, yet I have not heard or read of any carrying out the thought to its natural conclusion, and inquiring whether the dietetic use of much sugar could be charged with the power of inducing cataract in those partaking of it. Latterly I have directed some attention to this point, and from what I have observed, and guided by analogy, I affirm that a certain number of cases of cataract, which we meet with in daily life, are indeed due to the prolonged use of much sugar.
The diabetic cataract is not due to a primary disease of the lens; it is not due to the hepatic or neural lesion underlying the disease, known to us as diabetes; it is due to the presence of sugar in the blood of the diabetic patient.