by the mouth through the mouth-piece some twenty or thirty times. The cap may then be replaced, and the tube removed altogether and examined at once, or retained for a time. Before microscopical examination the cap is removed, and the tube, the stopper still in it, is placed near a fire, or at a little distance from the flame of a spirit-lamp, in order to allow the chloride that may be formed to crystallise on the slide. When this is effected, the stopper is removed, and the slide is ready to be placed under the microscope for examination. The advantages of this tube are: 1st, that it is portable, 2nd, that in use nothing but the expired air of the patient comes into contact with the acid; and 3rd, that the evaporation and crystallisation are performed with as little exposure to the air as is possible.

A few experiments with this tube on healthy persons will indicate that, under most circumstances, crystals of chloride of ammonium are produced after expiration through the tube when the slide is charged with hydrochloric acid. But practice soon points out the extreme amount of the crystalline body that can be produced in health by a fixed number of expirations; so that comparisons between this production, and that occurring after the administration of ammonia, are easily and practically learned. In health, the crystalline deposit is thin and scattered; after free administration of ammonia, if the action of the skin or kidneys, or of both, be not profuse, the slide is frosted with the salt.

In administering ammonia, it is essential that the

medicine be pushed to the extent of showing a free evolution in the breath. But, while this point is to be insisted on, it is essential that there be a limit to the administration; for if it be carried to an extreme, two evils are induced. In the first place, the ammonia by its presence stops, to a considerable extent, the process of oxygenation; and, secondly, it acts by its solvent power on the blood-corpuscles. It is well, therefore, nay requisite, also to examine the blood microscopically during the administration; when, if the red corpuscles while still in motion present the appearances marked A, B, C, D, E, F, G, in figure 3, plate II—that is to say, if the discs be crenate, or irregular, or transparent, or collapsed, or oval, or very diffuse-the indications are given that the alkali is becoming dangerous, and requires to be suspended.

Whether the above methods of treatment (I mean the hot air bath and the administration of a bloodsolvent) are the best and only means of treatment altogether, I cannot say. Time may come when an antidote immediate in its effects will be discovered, and which shall play to scarlet fever the same part as quinine plays to ague. But meantime, while the remedy is wanting that shall destroy the organic poison, or guard the body against it, the only two rational points of practice are the depuration of the secondary poison through the skin, and the administration of an alkaline solution having the properties of holding and retaining the blood in solution. We certainly address ourselves by these measures to the

effects of the secondary products of diseased functions, but our proceedings are none the more on that account to be ignored or despised.

If I have not named other plans of treatment, nor specified different and distinct treatments for differing types of the disorder, the omission must not be considered as accidental nor as inadvertent. The truth is that, in recasting the history of cases through three extensive epidemics, in which every variety and shade of treatment from bloodletting on the one side, to alcoholism on the other, was tried, I can extract no truth worth noticing as to treatment; except in those examples where, together with the induction of free elimination from the skin, and the administration of ammonia, fresh air and simple nutritious drinks, without stimulants, were supplied. In these examples, this treatment has seemed to me efficient; and I have now seen, in some twelve most severe instances, such unexpected results from it, that, without making out any pretence in it to a specific remedial system, I may speak of it as an approach towards a solution of the question of treatment, as it stands on the line of our present knowledge. I do not think cases need be considered in regard to their type for this treatment, but rather that, whenever treatment in any case is required, the general character of it is dictated in the outline I have given.

The local treatment, applied usually to the throat in scarlet fever, on which some practitioners exercise so much labour, is to my mind a secondary consideration. True, where there is much secretion, we

may avert asphyxia by removing the secretion by a sponge or piece of lint. But I am sure I have known great injury done by the excessive application of caustics; and, while I can recall no case in which the throat improved under any treatment while the general systemic mischief remained, I have never seen a throat, however disorganised, that did not recover when the general symptoms led the way to convalescence. There are, nevertheless, considerations which may lead to the employment of deodorising gargles or washes with much benefit. A weak solution of chloride of lime, or of chlorine water, is well adapted to such purpose; but the most elegant, as well as the most effectual deodorising gargle I have used, is made as follows:

Of solution of peroxide of hydrogen, containing ten volumes of
oxygen, six ounces; tincture of myrrh one ounce; rose
water five ounces.

This gargle may be used ad libitum: it is very refreshing to the patient, and it removes the offensive secretions readily. In the case of young children who are unable to use a gargle, the throat is always easily washed by holding the little patient with the face downwards, and by pumping the solution over the surface of the fauces through a bit of gumcatheter, from a double acting India-rubber bag.

The preventive treatment of scarlet fever consists, first, in the carrying out of a rigid quarantine. Dr. Blackburn, half a century since, entirely proved that even in a boarding-school the disease would not spread, if the patients were confined to one room, and

the attendants were kept altogether away from the unaffected. Nor should the separation of the patient be confined merely to the time when the acute symptoms are being manifested; it should extend to at least a month after the date of the commencement of the attack. In the second place, the room of the patient should be kept sedulously ventilated, as well for his own safety, as for that of others. Lastly, as it is obvious that almost every material object, in contact with the patient, is capable of holding the poison, all articles of clothing and furniture should be thoroughly disinfected by the best of all disinfectants, heat at boiling point, before the susceptible body of another person approach them. With strict adherence to these simple rules, the disease, according to my experience of it, can be kept safely from propagation.

RESUME.

The propositions embodied in this contribution to the clinical history of scarlet fever are as follow:

1. Age. Scarlet fever is most frequent during the third and fourth years of life. It declines rapidly after the fifth year, being nearly three times less common from five to ten, rather more than twelve times less from ten to twenty, nearly thirty times less from twenty to forty, and one hundred and one times less after forty, than in that period of life which is embraced in the first four years. The explanation of this fact lies, not in supposing that age, per se, exerts any decisive influence, but in the