88 MEDICAL JURISPRUDENCE menstruation, abortion, parturition or haematemesis, whether it is from an assailant or a victim, and whether it was shed before or after death. But it is not helpful in solving these problems. It gives an idea about the size, thickness and colour of the stain and perhaps the direction from which the blood came. It is difficult for a medical man, even of much experience, to offer an opinion as to the age of blood stains. It is a fact that medical men in India do sometimes make far too definite statements in this matter. A young in- experienced doctor is apt to make such a statement under the impression that the court would think him a fool if he did not give a definite opinion as regards the age of a stain, but he should remember that it is practically impossible to say more than that the stains are fresh or not fresh. The appearances of stains as to whether they are fresh or not depend on the colour and the nature of the material. Recent stains on a white cloth are of a brightjred colour which, on exposure to light and air, gradually changes to reddish-brown in about twenty-four hours, especially in hot weather, and subsequently changes to dull brown ; this is fairly permanent but in the course of time it may become Black. 4It is, therefore, evident that an expression of opinion as to the age of blood from consideration of its colour is well-nigh impossible. Dry stains have a starchy feel on cloth composed of a thin fabric, such as cotton, silk or linen. Stains of recently effused blood on a hard substance, such as stone, iron, steel or any other metal, have a darX_shining appearance, while dry and old ones have often a cracked^or^fissured look. Recent stains are also more soluble in distilled water or normal saline than old ones in which haemoglobin gradually changes to methsemoglobin and finally to insoluble haematin. Blood effused during life, when dry, can be peeled off in scales owing to the presence of fibrin in its coagulum, but it is liable to break up into a powder if shed after death. The recently shed arterial blood is bright red in colour, and the venous blood is dark red, but this difference can hardly be distinguished in a dried stain. The arterial blood is seen in the form of jets or sprays, which have an appearance of elongated, pear-shaped marks which may be compared to ' signs of exclamation'. The jets may be projected to a distance of three to four feet, if effused from small arteries. _The arterial blood is always shed during life, as blood-pressure in arteries falls to zero after death. It is not possible to state from the appearance of stains whether they are of menstrual blood or from any other source. It may, however, be noted that stains due to menstrual blood and haematemesis are acid in reaction owing to the presence of vaginal and gastric secretions, but in blood stains the ordinary method of testing the reaction is hardly applicable. ^B^xarai- nation under the microscope will determine the nature of the source. ]KTis not correct to suppose that menstrual blood does not clot; the vaginal mucous secretion may only delay clotting. Whether blood stains belong to an assailant or a victim can be determined only from circumstantial evidence by examining an article of clothing. If the stains are on the inner side of a garment it is very probable that they belong to a victim, but, if on the outside, they may belong to an assailant, thotigh not necessarily so, as the stains would be found on the outside of a garment worn by a man who received a blow on the head, while standing. Again, an assailant may not show any stains of blood if he is so standing as to avoid splashing from the outflow of blood while inflicting an injury. Besides, he may have changed the clothes or may have washed them, but blood stains which are faint and invisible by ordinary light after the washing of the clothes are rendered quite visible when they are exposed to the ultra- violet rays or when they are photographed with infra-red sensitive plates.