An interesting exception to the rule is that the serum from the blood of anthropoid apes gives a pronounced reaction with serum that has been made specific for human blood, and _vice versa_. As it is not possible to carry out control tests with an indefinite number of animals a positive result obtained in the examination of a particular stain justifies a report that the blood was (_e.g._) probably human blood and certainly not that of any common domestic animal. On the other hand, the results of a negative test justify a much more positive statement. Thus on the first occasion in which evidence was given as to the results of this test, which was in a criminal case in France in 1902, the prisoner had asserted that certain incriminating stains had been caused by the blood of a rabbit. A serum specific for rabbit's blood serum was therefore prepared, and the stains dissolved and tested as described above. No sign of precipitate was obtained within thirty minutes after applying the test and evidence was therefore given that the stain certainly did not consist of rabbits' blood. On the other hand, a serum made specific for human blood gave an immediate precipitate with the solution of the stain, which, therefore, in all probability consisted of human blood. Although this method of testing blood-stains has been used on the Continent for several years, it is only within the past twelve months that it has been employed in a criminal case in this country. Apparently the first occasion was in the recent trial of Mark Wilde for the murder of Mr. George Storrs, a mill-owner, at Gorse Hall. Evidence was given that old stains were present upon the outside of the sleeve of the prisoner's blue serge coat, although they were not visible to the naked eye. These were found to consist of mammalian blood, and the serum test for human blood gave a positive reaction. It was, of course, impossible to form any idea as to the age of the stains, and the witness, Dr. Wilcox, refused even to give an estimate upon this point. A simple method of applying the serum test has recently been discovered. A small quantity of human serum is placed into a series of tubes, and into each of these is next introduced one drop of the fresh blood of different animals diluted with salt solution, or of the dried blood dissolved in that liquid. The tubes are now allowed to stand for thirty to forty-five minutes and are then examined. If in the case of the blood of unknown origin there is a faint red precipitate (of coagulated blood) leaving the upper liquid quite clear, the blood is of human origin. On the other hand, the blood of other species of animals will have dissolved in the human serum, colouring it red. [Illustration: RABBIT'S HAIR] [Illustration: HORSE HAIR _By kind permission of Messrs. Scott Greenwood & Co._]