—Dr. Richardson's papers published in "Nature," and designed to prove the advantage, and in fact the real necessity of experimenting on animals in order to be ready to save human life, contain many interesting facts and deserve to be widely read in view of the current discussion as to the propriety of permitting the practice of vivisection. The following case affords conclusive proof of the learned and humane physiologist's argument. He says: "Dr. Weir Mitchell of Philadelphia, in the year 1869, made the original and remarkable observation that if a part of the body of a frog be immersed in simple syrup, there soon occurs in the crystalline lens of the eyeball an opaque appearance resembling the disease called cataract. He extended his observations to the effects of grape sugar, and obtained the same results. He found that he could induce the cataractic condition invariably by this experiment, or by injecting a solution of sugar with a fine needle, subcutaneously, into the dorsal sac of the frog. The discovery was one of singular importance in the history of medical science, and explained immediately a number of obscure phenomena. The co-existence of the two diseases, diabetes and cataract, in man had been observed by France, Cohen, Hasner, Mackenzie, Duncan, Von Graafe, and others, and Von Graafe had stated that after examining a large number of diabetic patients in different hospitals, he had found one-fourth affected with cataract. Before Mitchell's observation there was not a suspicion as to the reason of this connection, and a flood of light, therefore, broke on the subject the moment he proclaimed the new physiological fact. Still more, Mitchell showed that the cataract he was able to induce by experiment was curable also by experiment, a truth which will one day lead to the cure of cataract without operation. Then, but not till then, the splendid character of this original investigation, and the debt that is due to one of the most original, honest, laborious workers that ever in any age cultivated the science and art of medicine, will be duly recognized." Upon receiving intelligence of this discovery, Dr. Richardson undertook experiments to discover the cause of this dependence of cataract upon diabetes. He found that whenever the specific gravity of the blood was raised to ten degrees above the normal standard, and remained so for a short time, cataract followed. He also found that the disease so produced could be cured by removing the salts which had been introduced into the blood. This certainly points to a cure for cataract which shall be really radical, and adds another to the results which justify, even upon humanitarian grounds, physiological experiments, at the expense of the animal creation, within prescribed limits.
—Mr. Sorby has lately made some calculations of the probable size of the invisible atoms which compose material substances. Dr. Royston Pigott determined that the smallest visual angle which we can well appreciate is that covering a hole of 11.4 inches diameter at a distance of 1,100 yards. This corresponds to about six seconds of an arc. In a microscope magnifying 1,000 diameters this would make visible a particle one-three-millionth part of an inch thick. But Mr. Sorby is inclined to think that a size between 1/80,000 and 1/100,000 of an inch is about the limit of the visibility of minute objects, even with the best microscopes. Now, taking the mean of the calculations made by Stoney, Thomson, and Clerk-Maxwell, we have 21,770 as the number of atoms of any permanent gas required to cover one-thousandth of an inch, when lying end to end. By a series of calculations which produce numbers entirely beyond human conception, (10,317,000,000,000 atoms in 1/100,000,000 of a cubic inch, for instance) he reached the conclusion that there are in the length of 1/80,000 of an inch (the smallest visible object) about 2,000 molecules of water, or 520 of albumen, and therefore, in order to see the ultimate constitution of organic bodies, it would be necessary to use a magnifying power from 500 to 2,000 times greater than those we now possess. With this result settled, he was able to make one of those radical predictions which are so rarely possible to the careful scientist; namely, that the atom will never be seen by man. It is not that instruments cannot be made powerful enough (though that is no doubt true), but that the waves of light are too coarse to distinguish the limits of such an extremely small distance. To see atoms we should need light waves only one-two-thousandth of their actual length. At present we are as far from that attainment as we are from reading a newspaper, with the naked eye, at the distance of one-third of a mile.