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 The Scientific Detection of Crime. death occurred at the end of nine days, — a long time, — and as the presence of arsenic in the stomach and intestines was simply the result of absorption and preparatory elimination, the woman was acquitted. When we devote ourselves to the exami nation of blood found on the body of the suspected person, the furniture of the room, or the textile fabric, the microscope is of invaluable service. We have several points to consider, and various' questions of interest arise : 1. Is the substance found blood, and is it human blood? 2. Was it accidentally deposited upon the person or not? This first piece of information is often difficult to obtain, as there are many things which closely resemble blood, — among these the iron salts, and various dyes. We have to be very careful, in re moving stains from knife-blades, to avoid removing rust as well. After we dispose of these doubts, and when we decide the spot to be blood, we have to determine whether it is human blood or not. There has been much discussion in regard to this matter, and though some writers say that there is marked difference between the size of the blood-corpuscles of man and the other mammalia, it has been the general opinion of able investigators that there is none. There are certain grand distinctions, how ever, where there is an absolute certainty in telling whether the blood is from mam malia, birds, fish, or reptiles. The corpus cles of the three latter are all elliptical, while the former are circular. It occasion ally happens that the criminal becomes

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caught by his own attempts to explain away the appearance of blood upon his clothing. A man who was suspected of murder was arrested, and, when questioned in regard to some bloody spots upon his coat, attempted to account for them by saying that he had been cleaning fish. The microscope revealed the fact that the corpuscles were round and not oval. All blood-corpuscles become smaller in dried blood, and this should be taken into account when an examination is made. This ques tion of difference in the size of the corpuscles has been such a perplexing one that various other tests have been thought of. Numer ous German investigators have attempted to solve the problem, and have advanced the theory that a certain coloring substance of blood, hcemoglobiiie, from different animals, will crystallize in a different way. This test is not so exact as it was originally thought to be, and we are again in want of a new plan. An infallible test, however, is obtained by the spectroscope, that most valuable of instruments. It is competent to detect the smallest trace of blood, even after clothing has been washed. Sorby be lieves that even the one-thousandth part of a grain of blood can be recognized. Surely, with such an instrument as this at our disposal, the chances for the suspected per son are very small. With the new dis coveries that are being made every day, and the valuable agents already in our hands, the statistics of crime and the cer tainty of arrest will be greatly increased in the future. — Allan M. L. Hamilton, M.D., Appletoris Journal.