The judge, in his summing up, made the following comments upon the evidence: "The witness had said that the blood upon the knife could not be the blood of an animal as stated by the prisoner, and took upon himself to say it could not be the blood of a dead animal; that it was living blood and that it was human blood; and he had shown them the marvellous powers of the modern microscope. At the same time, admitting the great advantages of science, they were coming to great niceties indeed, when they speculated upon things almost beyond perception, and he would advise the jury not to convict on this scientific speculation alone." The jury found the prisoner guilty upon evidence other than this "scientific speculation," the novelty of which probably prevented the judge from accepting it as a demonstration of facts which might be verified or disproved. The application of a remarkable discovery in physiological chemistry has now made it possible to determine whether a blood-stain consists of the blood of any particular kind of animal. In 1898 it was discovered by Bordet that on injecting serum of cow's milk into a small animal, such as a rabbit, which was then killed after a lapse of some weeks, the serum separated from its blood would produce a precipitate in cow's milk. This discovery was supplemented by Wassermann, who, in 1900, found that it was possible in this way to distinguish between the milk of different kinds of animals, and he suggested the name _precipitines_ for these specific precipitating agents formed in the sera of animals. Then Dr. von Rigler showed that the method might be employed to distinguish between the flesh of different kinds of animals. [Illustration: GOAT'S HAIR A. Apex of Fibre. B. Root. C. Fibre showing central canal or medulla.] [Illustration: COW'S HAIR A and B. Fibres showing central canal or medulla. C. Apex of Fibre. _By kind permission of Messrs. Scott Greenwood & Co._] He prepared a 20 per cent. aqueous extract from the flesh of seven different species of animals, and injected small proportions of these beneath the skin of rabbits at intervals of three days. After a month the animals were killed, and the serum of the blood separated in a centrifugal machine. In each case the specific sera were added to the clear filtered aqueous extracts of the flesh of the respective animals, and the tubes examined after the lapse of a specified time. It was found that the sera only gave a turbidity or precipitate with the corresponding extracts. Thus the serum from the rabbit which had been treated with an extract of horseflesh only gave a reaction with preparations of horseflesh, and not with those of venison, beef, mutton or pork. In like manner, the serum from a rabbit that had been treated with an extract of rabbit's flesh, only reacted with extracts of rabbit's flesh, and not with those prepared from the flesh of cats, horses, or other animals, and so on.