The injection into the veins of medicinal agents is dangerous or not, according to the character of the material so used. Numerous experiences have demonstrated the safety of ammonia injections, and Prof. Ore, of Bordeaux, has practiced the intra-venous injection of chloral to induce anaesthesia. Formerly, before the introduction of the hypodermatic method, the injection of medicines directly into the blood was suggested and occasionally practiced in cases of asphyxia, in the collapse of cholera, in the insensibility due to narcotic poisons, etc. At present this method is restricted within narrower limits. Some remarkable results have been obtained by the injection of a saline solution into the veins in cases of the collapse of cholera. The first trials with the intra-venous injection of salines were made in 1832 with little success, but in succeeding epidemics greater confidence was felt in the remedy, and in 1866 it came to be used quite freely. For example, in 1867, Little, reporting on his experiences, gave an account of five recoveries out of twenty cases in an apparently hopeless state. During the epidemic of 1892 at Hamburg, Havre, Paris, Berlin, and elsewhere intra-venous injections were practiced on a large scale and with a greatly increased measure of success, so that it has now become a practice of the first importance in the treatment of the algid stage of cholera. The same method is also employed in the treatment of haemorrhage instead of transfusion of blood in cases of sudden heart-failure, in diabetic coma, and other states.

The injection of salines into the veins is also entitled intravenous infusion. By means of a suitable apparatus the fluid is poured into the veins. The simplest arrangement for this purpose consists of a reservoir for containing the requisite amount of solution, a flexible tube for conveying the solution, and a suitable perforated needle for transfixing the vein. There are various patterns of instruments for effecting the intravenous injection, but if the right conditions are complied with the least complicated may be used with complete success. The fluid must be a saline solution, so as not to coagulate the blood or to dissolve the blood globules; it must be sterilized, so as not to convey germs; it must be at the right temperature; and it must be passed into the blood without at the same time carrying globules of air. The amount to be inserted need not exceed a few ounces. Even when the loss of blood has been enormous, or when the serous discharges have brought on collapse, a few ounces of saline fluid suffices to restore the circulation. Recent experiences have apparently shown that even in great loss of blood it is not so much the blood itself that is needed, but a small quantity of serous fluid apparently suffices.

Hayem recommends the following formula as a close approximation to the composition of blood-serum :

Water............ .................................. 3 oz.

Hydrate of sodium....................................  15½ grains.

Chloride of sodium....................................  80 grains.

Sulphate of sodium.................................... 6½ drachms.

The temperature of the fluid injected should not be greater than 100° Fahr., and the amount which experience has shown to be well supported is not greater than two litres, and usually one litre (a quart) is sufficient for one operation. The fluid should be injected slowly, according to Potain, at such a rate that not more than 20 cubic centimetres pass into the blood in a second. Dr. Histon Fagge has recently reported a case of diabetic coma, in which the injection of twenty-six ounces of a warm solution of salines (phosphate and chloride of soda) produced an astonishing improvement in the condition of the patient. A suitable saline solution for intra-venous injection may be made of phosphate, carbonate, and choloride of sodium, dissolved in water at the temperature of 100° Fahr. until the specific gravity of 1020 is attained. The instruments employed for transfusion of blood may be used for the intra-venous injection of salines.

Halford, of Australia, has successfully practiced the injection of ammonia into the veins, in the treatment of the bite of venomous snakes. He employs one part of the stronger aqua ammonioe to two parts of distilled water, the injection being made with an ordinary hypodermatic syringe. A vein in a convenient situation is selected, the needle is inserted into it, and the solution of ammonia is thrown in gradually. The operation may be repeated, as necessary, the guide to the repetition of the injection being the state of the circulation. Fayrer shows that this practice is not successful in the systemic condition caused by the bite of the venomous snakes of India, and the special committee of the Medical Society of Victoria, appointed to investigate the subject of the intra-venous injection of ammonia, report adversely to the claims of Halford. The proposer of this expedient has, at least, demonstrated the safety of the intra-venous injection of ammonia; and, although his first claim has been shown to be incorrect, the method itself has been utilized in other maladies: for example, in chloroform asphyxia, opium narcosis, hydrocyanic-acid poisoning, etc. Failure of the heart's action and thrombosis of the pulmonary artery, post partum, are also indications for the intra-venous injection of ammonia.

Attention has been called elsewhere to an instance reported by Dr. Eskridge, which is remarkable both as to the injection and as to the results obtained. By an error, undiluted aqua ammonia was injected directly into the blood-current, but no untoward effects accompanied or followed, and the curative action exerted in the malady was most successful. Although, at one time, the escape of ammonia was supposed to be the cause of the coagulation of the blood, and although this is no longer held as a theory, it has served to demonstrate the fact that such intra-venous injections can be practiced without ill effects, immediate or remote.