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 of the bones, as happens in what is known as concussion of the brain. Contusions which do not divide the skin may fracture the skull; or the inner table of the skull may be fractured without the outer being broken or depressed. Even wounds of the scalp may prove fatal, from inflammation extending towards the brain. Punctured wounds of the head are more dangerous than cuts, as more likely to excite fatal inflammation. When the brain and its membranes are injured, all such wounds are generally fatal. Wounds of the face or organs of sense are often dangerous, always disfiguring, and productive of serious inconvenience. Wounds of the neck are always serious whenever more than the skin is divided. The danger of opening large blood-vessels, or wounding important nerves, is imminent; even the division of a large vein in the neck has proved immediately fatal, from the entrance of air into the vessel, and its speedy conveyance to the heart. A blow on the neck has instantly proved fatal, from injury to an important nerve, generally the pneumogastric or the sympathetic. Dislocations and fractures of the bones of the neck prove instantly fatal. Wounds of the chest are always serious when the cavity is penetrated, though persons may recover from wounds of the lungs, and have even survived for some time considerable wounds of the heart. This last is an important fact; because we are not always to consider the spot where the body of a person killed by a wound of the heart, and apparently remaining where he fell, is found as that in which the fatal wound was inflicted. Instances have occurred of persons surviving severe wounds of the heart for several days. Broken ribs are never without danger; and the same may be said of severe contusions of the chest, from the chance of inflammation extending inwards. Wounds penetrating both sides of the chest are generally considered as fatal; but possibly there may be recovery from such. Wounds of the abdomen, when they do not completely penetrate, may be considered as simple wounds, unless when inflicted with great force, so as to bruise the contents of the abdominal cavity; in that case they may produce death without breach of surface, from rupture of some viscus, as sometimes happens from blows or kicks upon the belly. Wounds injuring the peritoneum are highly perilous, from the risk of severe inflammation. Wounds of the stomach or intestines, or of the gallbladder, generally prove mortal, from the effusion of their contents into the peritoneal cavity producing fatal inflammation. Wounds of the liver, spleen or kidneys are generally soon mortal, from the great vascularity of those organs. Wounds of the extremities, when fatal, may generally be considered so from excessive haemorrhage, from the consequences of inflammation and gangrene, or from the shock to the system when large portions of the limb are forcibly removed, as in accidents from machinery, and in wounds from firearms.

Blood Stains.—The examination of blood stains is a frequent and important operation in criminal charges. Blood stains when fresh and abundant can be recognized without difficulty, but when old, or after being acted upon by certain substances, their identity is not readily determined.

The tests which may be applied to a suspected stain consist of: (1) The microscopic test. A portion of the stain is soaked in a drop of some fluid which will soften and cause separation of the dried blood corpuscles without altering their characteristic appearance. Such fluids are solutions of glycerin and water of a specific gravity of 1028 or 30% caustic potash. The recognition of blood corpuscles affords evidence of the nature of the stain. (2) Chemical tests. (a) Heat applied to a solution obtained by soaking some of the stained fabric in cold water. A blood solution is red, and loses its red colour on application of heat, while at the same time a buff-coloured precipitate is formed. (b) On applying a drop of freshly prepared tincture of guaiacum and then some ozonic ether or peroxide of hydrogen to the stain, a blue colour is obtained if blood be present. Many other substances, however, give the same reaction. (c) If, even to the smallest particle of dried blood, a fragment of common salt and some glacial acetic acid be added, and the latter is then heated to ebullition and allowed to evaporate away, small brown rhomboid crystals—haemin crystals-will be found to have formed, and they can be recognized under the microscope. (3) Spectroscopic test. A solution of blood obtained from a stain will show a spectrum having two dark bands between Fraunhofer's lines D and E (oxyhaemoglobin). On adding ammonium sulphide to the solution the haemoglobin is reduced and only one broad dark band is seen (reduced haemoglobin). On adding caustic potash to a solution of blood, alkaline haematin is formed, and this again is transformed on the further addition of ammonium sulphide into reduced haematin or haemochromogen, which gives a very characteristic spectrum of two dark bands situated in the yellow part of the spectrum. The production of these three different spectra from a red-coloured solution is characteristic of blood. Old blood stains are insoluble in water, whereas recent stains are readily soluble in cold water, yielding a red solution. The application of hot water or washing with soap tends to fix or render blood stains insoluble. Vegetable dyes may likewise give red solutions, but they may be distinguished from blood by the addition of ammonia, which alters the colour of the former, but rather intensifies the red colour of a blood solution.

The differentiation between human blood stains and those produced by the blood of other animals, more especially domestic animals, is a matter of great importance to the medical jurist. When the blood stain is fresh, measurement of the corpuscles may decide the question, but in the case of dry and old stains it is impossible to make the distinction. A method has been discovered, however, which enables the distinction to be made not only between human blood and that of other animals (with the exception of Simiidae), but also between the bloods of different animals. The method depends upon the fact that if an animal (A), such as a dog or rabbit, is inoculated with the blood or serum of another animal (B), then the blood or serum of A is found to produce a specific reaction (namely, the production of a cloudiness or precipitate) when added to a solution of the blood of a similar animal to B, and that species of animal only. If, therefore, human blood serum is injected into an animal, its blood after a time affords an “antiserum” which produces the specific reaction only in human blood solutions and not in those formed from the blood of other animals.

10. Poisoning.—There is no exact definition of a (q.v.). Popularly, substances which destroy or endanger life when swallowed in small quantity are called poisons, but a scientific definition would also include many substances which are injurious to health in large doses or only after repeated administration, and which act not only when swallowed, but also when taken into the system through other channels, e.g. the skin or the lungs. The branch of science which relates to poisons, their nature, methods of detection, the symptoms produced by them, and treatment of poisoning, is called Toxicology, and is one of the most important subjects included under the term Medical Jurisprudence.

The medical evidence in cases of poisoning rests upon—(1) the symptoms produced during life; (2) the post mortem appearances; (3) the chemical analysis and detection of the substance in the body, or in the excretions and vomited matters, or in articles of food; (4) experiments on animals in the case of certain poisons where other conclusive evidence is difficult to obtain. The treatment of cases of poisoning will vary according to the substance taken, but the general principles which should be followed are: (a) to get rid of the poison by means of the stomach-pump, or by washing out the stomach with water through a soft rubber tube, or by giving an emetic such as mustard, sulphate of zinc, ipecacuanha; (b) to neutralize the poison by giving a substance which will form with it an innocuous compound (e.g. in the case of the strong acids by administering magnesia or common whiting), or which has an opposite physiological action (e.g. atropine in opium poisoning); (c) to promote the elimination from the body of the poison which has been already absorbed; (d) general treatment of any dangerous symptoms which appear, as by stimulation in collapse or artificial respiration in asphyxia.

Food Poisoning (see also ).—Foods may prove noxious from a variety of causes: (1) The presence of metallic poisons, as in peas artificially coloured with copper salts, in tinned foods from dissolved tin salts, &c. (2) The contamination of any food with the specific germs, of disease, as for example, milk infected with the germ of enteric fever. (3) The presence in meat of parasites, such as the Trichina spiralis, or of disease in animals, capable of transmission to man, such as tuberculosis, or the presence of poison in the flesh of animals which have fed on substances harmless to them but poisonous to human beings. Grain may be infected with parasitic fungi of a poisonous character, as for example Claviceps purpurea, causing epidemics of ergotism. (4) Foods of various kinds may contain saprophytic bacteria which elaborate certain poisons, either before or after the food is taken. It is chiefly in relation to food-poisoning from the last-mentioned cause that our knowledge has been increased in recent years.

Many cases of food-poisoning, previously of mysterious origin, can now be explained by the action of bacteria and the products which they give rise to—tox-albumoses, ptomaines, toxins—by splitting up proteid substances. It is not necessary that the food should show evident signs of putrefaction. It may not do so, and yet on being eaten produce violent symptoms of gastro-intestinal irritation almost immediately, followed by various nervous symptoms. In such cases a chemical poison, developed by putrefactive bacteria before the food was eaten, quickly acts upon the system. On the other hand, symptoms may not appear for many hours after ingestion of the food, and then come on suddenly and with great