Page:The American Cyclopædia (1879) Volume II.djvu/760

 740 BLOOD STAINS lor says that he has obtained clear evidence of their existence in a small quantity of blood, which had been kept in a dry state for three years. Dr. Charles Robin has discovered the presence of red corpuscles on clothes in stains of eight or ten years' duration. Prof. Jeffries Wyman says that in blood which had been allowed to dry in masses he has failed to find the red corpuscles, while, on the contrary, the white or colorless corpuscles may be softened out after they have been dried for months, and their characteristic marks readily obtained. He found it easy to detect them in blood which had been dried for six months. Dr. Robin has given a drawing representing what the micro- scope showed in a solution of a stain found on the blade of a knife. No red corpuscle is fig- ured, while on the contrary many colorless ones are. But the mere fact of the presence of col- orless corpuscles, with nearly the same appear- ance that they have in fresh blood, is not suffi- cient to prove that a stain is due to blood, be- cause the chyle and lymph corpuscles, those of pus, and even some of those of mucus, are similar to the white corpuscles of the blood. When clothes have been washed after having been stained with blood, nearly or quite all the cor- puscles are removed, or so much altered that their presence cannot be ascertained positively. But chemistry may then render it very proba- ble that there has been blood on such clothes, by detecting in them iron and a coagulable organic matter. If blood stains are on the blade of a knife, the microscope and chemi- cal reagents may enable us to distinguish them from rust. Usually, when the knife is heated, a blood stain may be peeled off, leaving a neat metallic surface where it was ; it is not so with rust, which remains almost unaltered. Besides, when the stain is washed, it leaves a much smoother surface if it is due to blood than if it comes from rust. Usually in this latter case there is a peculiarly dentated surface, the pres- ence of which leaves no possibility of a mistake. In a case where Daubrawa was requested to ascertain the existence of blood stains on a knife which was suspected to have been used in the commission of a murder, this instrument, having lain a long time in a damp place, was rusted, but there were certain bright spots free from rust, and surrounded by it. On heating the point of the blade these spots scaled off, while the rust remained adherent ; and on immersing the knife in diluted hydrochloric acid, the bright spots remained unaltered while the rust readily dissolved. Some of the re- agents which serve to detect blood were then employed, and it was found that the bright spots were really covered with blood, which had prevented the formation of rust. In an- other case in which a man had been accused of murder, an examination of a knife covered with red spots, and found concealed behind a piece of furniture, proved that the stains were due to rust produced by lemon juice. Blood may- be detected even on a stone. Prof. Lassaigne ascertained its presence a full month after it had been shed on a pavement of soft freestone, which had been exposed to the action of air, of rain, and of the sun. The color of the stain had passed to a dirty green, with a reddish tint hardly discernible. In a place where stains of blood are suspected to exist, and where none are found by daylight, the search for the red spots must be made by artificial light. In a case where Ollivier d' Angers had vainly tried by daylight to find stains of blood on the floor and on the paper hangings of a room, he de- tected many by candlelight. II. When it is decided that a red stain is due to blood, it re- mains to be ascertained if the blood is that of a man or of an animal. Chemistry in such an examination is of little avail. The physical character of the red corpuscles of the blood is almost the only guide. It has been said, how- ever, that some reagents may develop in the blood such a smell that it is easy to determine not only from what animal the blood comes, but also whether it is that of a man or of a woman. When sulphuric acid is added to the blood of an animal or of a man, it gives rise to a smell which has been said to be just the same as that of the individual that furnished the blood. The chemist (Barruel) who dis- covered this fact was almost always able to make out by this means what was the source of blood sent to him ; so were Colombat and some other physicians; but decisive examinations have shown that very few have the organ of smell sensitive enough for this purpose. In man and all the mammalia (except the camel tribe), the red corpuscles are circular, flat disks, while in most fishes, in reptiles, birds, and cam- els, they are oval. In a case mentioned by Taylor, it was suggested in the defence that the blood stains on the clothes of the prisoner were due to his having killed some chickens. The shape of the globules negatived this part of the defence. In another case the blood was alleged to be that of a fish; this was also dis- proved by the shape of the corpuscles. Dr. H. Bennett of Edinburgh states that a patient having bronchitis had put bird's blood in her sputa, and that after the microscope had shown this fact she was greatly surprised that it had been discovered, and confessed that she had done it for the purpose of imposition. On looking at the table of the dimensions of the blood corpuscles (see BLOOD), it will be found that the blood disks of man are larger than those of all the domestic animals. To cover the extent of a linear inch requires 3,200 of the red corpuscles of a man, 4,404 of those of a cat, and 6,366 of those of a goat. C. Schmidt thinks he has shown that by accurate meas- urements of the red corpuscles, the blood of all the common mammalia can be individually detected and also distinguished from that of man. He proposes to avoid the errors arising from a greater or a slighter evaporation, by drying the blood corpuscles before measuring them. He gives the following table :