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298   MEMORIES OF MY LIFE

delicate operations, my own part was confined to inserting cannulm and the like. At first Dr. Murie did all the dexterous and difficult work. He had been a traveller in company with Consul Petherick, far up the White Nile, and was then Prosector at the Zoological Gardens. I called on him to discuss the matter. A dead cobra was lying on his table, and on my remarking that I had never properly seen a poison fang, he coolly opened the creature's mouth, pressed firmly at exactly the right spot, and out started that most delicate and wicked-looking thing, with a drop of venom exuding from it, just in front of his nail. I thought that a man who was so confident of his anatomical knowledge and of his nerve as to dare such an act, must be an especially suitable person to conduct my experiments, and was fortunate enough to secure his co-operation.

I continued the experiments for another generation of rabbits beyond those described in the Proc. Royal Society, with equally negative results. Mr. Romanes subsequently repeated the experiments with my instruments, and they corroborated my own. So this point seems settled.

The laws of -Heredity are concerned only with deviations from the Median, which have to be translated from whatever they were measured by, whether in feet, pounds weight, intervals of time, or any other absolute standard, into what might be called " Statistical Units." Their office is to make the variabilities of totally different classes, such as horses, men, mice, plants, proficiency in classics, etc.

etc., comparable on equal terms. The statistical unit