that can be distinctly observed; under such conditions, to make sure that the spectrum is really that of reduced hæmatin, the band should disappear if the liquid be heated to 50° C. without agitating, and reappear on cooling. If the blood colouring-matter has been radically changed by putrefaction, the spectroscopic reaction of reduced hæmatin may be the only test by which the presence of blood can be proved.

As there is a possibility of the spectra of methæmoglobin and acid hæmatin being mistaken for one another, they may be readily distinguished by the addition of an alkaline reducing agent, when the methæmoglobin spectrum changes to that of reduced hæmoglobin, and the acid hæmatin spectrum to that of reduced hæmatin.

Where the amount of blood stain is small, the spectroscopic tests should always be resorted to before the chemical tests are employed. The spectroscopic tests above described constitute the most delicate and certain means of detecting minute quantities of blood.

Other colouring matters than blood.-According to Sorby, although certain other bodies produce absorption bands somewhat resembling those of oxyhæmoglobin, nothing gives a spectrum precisely similar, at all events, to the eyes of a practised observer. Thus, the colouring-matter of the petals of Cineraria gives two absorption bands; cochineal, madder, and other red dyes, dissolved in alum solution, also give bands somewhat resembling those produced by blood. All these colouringmatters may be distinguished from the latter in that their colours are not affected by heat, but are changed on the addition of a weak solution of ammonia. Stains from cochineal, kino, madder, logwood, red flowers, and fruits, and redwine stains do not stiffen linen and cloth in the way that blood does. Moreover, they do not respond to the guaiacum test. The coloured juices of red fruits and red flowers turn a blue or greenish colour on the addition of a weak solution of ammonia; a solution of blood is not appreciably altered in colour by that reagent. The coloured juices are neither

coagulated, nor is their red colour destroyed by boiling; a solution of blood is coagulated by boiling, and its red colour is at the same time destroyed.

It should be borne in mind that the stains of certain organic salts of iron, notably the citrate and the malate, may on the blade of a knife present a very strong resemblance to blood

stains. If the blade of a steel knife has been used in cutting fruit, such as oranges, lemons, or apples, and is then left. unwiped and exposed to the air, a stain of the citrate or malate of iron forms on the blade. Such stains have been pronounced on superficial examination, even by medical men, to be blood stains. The solutions obtained from these stains yield none of the reactions of blood. Iron-mould stains on linen are of a reddish-brown colour; they are insoluble in water and in solution of ammonia; they are readily dissolved by hydrochloric acid, the solution yielding the reactions for iron, but none of the reactions of blood. Red-paint stains have occasionally been mistaken for blood stains; they are insoluble in water, but are generally soluble in hydrochloric acid, the solution. yielding none of the reactions of blood.

The composition of a fabric upon which a stain is found should be determined by teasing a small quantity of it in glycerine and water, and examining it under the microscope (figs. 26, 27, 28, and 29).

16

WOUNDS AND MECHANICAL INJURIES

CHAPTER XXVI

Definition of a wound--Examination of wounds on the dead body-Distinction of wounds inflicted during life and after death-Bruises - Wounds produced by weapons-Incised wounds-Punctured wounds-Lacerated wounds-Contused wounds - Stabs.

THE surgical and legal definitions of a wound are not identical. In works on surgery a wound is generally defined as 'a recent solution of continuity in the soft parts, suddenly occasioned by external causes,' or, in the words of Wiseman, as a solution of continuity in any part of the body, suddenly made by anything that cuts or tears, with a division of the skin.' Both of these definitions involve a rupture of the skin or mucous membrane to constitute a wound. Such definitions would not regard as wounds ruptures of the liver or spleen, simple dislocations, simple fractures and burns, although these, from the medicolegal point of view, should be included in the definition of a wound. The definition is extended beyond that given by the surgeon by the words which follow in the statute- Whosoever shall, by any means whatsoever, wound or cause any grievous bodily harm to a person.' As a matter of fact, the last clause of this sentence fortunately obviates the necessity for defining whether a given injury is or is not a wound. In the past, owing to vague definitions being employed by some medical witnesses, acquittals have frequently taken place upon mere technicalities, or the grave offence of wounding' has been converted into the minor offence of 'common assault.'

From the legal point of view a breach of continuity of the tissues may be regarded as a wound, although neither the superjacent skin nor mucous membrane is involved in the injury. Simple dislocations, simple fractures, ruptures of viscera, such as the liver, spleen, bladder, &c., if suddenly caused by external violence, are in the legal sense wounds, although the skin may be in no way implicated in the damage. Perhaps the best medico-legal definition of a wound that can be given is as follows:-A wound is a breach of continuity in any of the structures of the body, whether external or internal, with or without a solution of continuity of the skin, suddenly caused by external violence.

Wounds dangerous to life. In reference to persons charged with wounding or attempting to murder, a medical man may be required by a magistrate to give a written or verbal opinion as to whether the wound is dangerous to life or not, in order that the magistrate may decide whether he is justified in detaining the prisoner in custody or in admitting him to bail. The interpretation of the words dangerous to life' is left to the medical witness, who, consequently, must be prepared to give clear and satisfactory reasons for the opinion he has expressed, the opinion being frequently submitted to a rigorous cross-examination by the counsel for the prisoner. The medical witness must only consider a wound dangerous to-life, in the legal sense, when that danger is imminent, such as in connection with wounds of any of the viscera, of a large blood-vessel, or in the case of a compound and depressed fracture of the skull. If the danger to life be only a remote one, and dependent on certain contingencies under certain circumstances, then the opinion given should be a qualified one. For instance, any wound, but especially a lacerated wound of the scalp, may be followed by erysipelas; a punctured or lacerated wound may be followed by tetanus. These complications, which may prove fatal, are not, however, necessary sequela of the injuries. The medical witness, in expressing an opinion as to the nature of the wound, should mention the possible occurrence of these

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