fitted for the purpose, for six hours consecutively, I obtained no evidence whatever of the formation of the chloride.

On the other side, a copious expiration of ammonia is common to many diseases. I have said that the breath of all inveterate smokers is ammoniacal, and this point in male subjects must always be borne in mind when the breath is tested. In both sexes I have met with excess of ammonia in the breath in chronic bronchitis, in typhus, in one well marked case of purpura, in various simple dyspeptic cases where the bowels were constipated, in uræmia, in a case of albuminuria, in the various stages of phthisis, and in abscess of the lung.

To arrive at an approximate idea as to the normal and abnormal amount of ammonia exhaled by the breath, practice is required, first with men in health and afterwards with men diseased. To attempt an absolute quantitative analysis in each case is impossible, not only from the time required for the task, but from the difficulty of calculating the amount of air altogether evolved in a given time by different persons. But simple practice with the microscope glass soon supplies the general fact.

For the detection of the expired ammonia, Dr. Reuling recommends logwood paper; * but the microscope test is as delicate as can be desired, is, after a little

The action of ammonia on hematoxylin was pointed out by Erdmann (vide Handwörterbuch der reinen und angewandten Chemie, Band III, Braunschweig, 1848.) Hæmatoxylin, when brought into contact with ammonia, is dissolved, forming a rose-red or clear purple solution when the mixture is made over mercury. If an acid is introduced, the colour becomes yellow, but there is no precipitate; and, by adding sulphuric acid, crystals of unchanged hæmatoxylin are formed. If air is allowed to enter the ammonia solution, the colour immediately becomes purple, and ultimately dark red and almost opaque. A part of the hydrogen in the hematoxylin combines with the oxygen of the air; and a new body is formed which Erdmann calls hæmatein.

practice, most manageable, and gives a general knowledge of quantity. The mere holding of a rod moistened with dilute hydrochloric acid is not a sufficiently delicate test in the majority of cases; but if, when the rod is thus used, there is distinct evidence of white fumes, the test is sufficient to show that the amount of ammonia expired is far beyond the normal proportion; and, as at once proving this fact, it is simple and valuable. The reddened litmus and turmeric tests are also useless in most cases, because carbonic acid is thrown off in excess as regards the alkali; but if in any case these tests show the presence of alkali, they are valuable as proving at once a condition seriously abnormal, and as denoting excessive alkalinity of the blood. In one case of typhus in a boy, I used a piece of fine white gauze stretched over a ring. This, saturated with the reddened litmus, was held over the mouth and nostrils; and the expired air, passing through the gauze, restored, during the acme of the disease, the colour to the litmus after ten or a dozen expirations. As recovery advanced, the test failed.

To avoid fallacies in the use of the microscope test, it is well to use an instrument as sketched below. It is

nothing more than a straight breast-pump with a microscope glass carried across the trumpet end. In using this, a drop or two of pure acid is placed in the

bulb (B); the microscope glass (A) is secured across the trumpet end with a band of India rubber, and the patient is made to breathe through the tube by his mouth at the long and fine end. The air thus comes in contact with the acid is passing over it in the bulb, and a part of the alkali is there fixed; but some of the acid and alkaline vapours also pass on together, and, as there is condensation on the microscope glass, a field of crystals is deposited on drying. The acid in the bulb, containing also water which has been condensed with ammonia, may also be collected, if required, and subjected to experiment. In the subjoined microscopic sketch, the crystals were taken from a specimen derived in the manner above stated from a healthy man.

Ordinarily, the ammonia evolved by the breath is in combination with carbonic acid; and if the carbonic acid is removed, as I have found by experiment on my own breath, evidence of the free acid and of the alkali may often be obtained simultaneously. To show this, it is simply requisite to place baryta water in a Wolf's bottle, to breath through this, and to connect a long escape tube from the bottle with a potash bulb tube containing a solution of litmus, slightly reddened with acetic acid. While the expired air is passing through the baryta water, the Wolf's bottle is immersed in water at 200° Fahr., so as to raise the temperature of the baryta water and prevent the absorption and fixation of the ammonia. The expired air must be gently driven through the fluids in both containing vessels; and, if much time elapses, the baryta water must be changed. In the end, not only will the evidence of the carbonic acid be given. in the baryta water, but the reddened litmus will have its colour temporarily restored.

The evolution of ammonia in cutaneous exhalation has been known, as I have already shown, for a long time. In seeking for its presence in this exhalation, I place the hand for a few hours in a large wide mouthed bottle, moistened on its inner surface with pure hydrochloric acid, and connected to the wrist by a broad India rubber band, so as perfectly to exclude the air. After the hand is withdrawn, the contained fluid is carefully poured out of the bottle into a watch-glass. A drop of it placed on the microscope glass and evaporated down, with the usual precaution to evaporate slowly that the salt formed may not sublime, yields full evidence of the crystals of the chloride.

In some diseases where the action of the skin is pro

fuse, the amount of ammonia exhaled is very considerable. From the bodies of the consumptive, during and after the colliquative perspirations, this evolution is most marked. In one case of this kind, I found the acid rod giving white fumes when held near to the cutaneous surface; and, indeed, the peculiar odour which attends the perspirations of the phthisical, and is so marked when the bedclothes are raised, arises possibly from this cause, being faintly ammoniacal in character. In the critical sweats of fever there is a similar exhalation.

From fresh urine in health, ammonia rarely goes off spontaneously,-at all events, in sixty examinations. of the vapour from healthy urine at the moment when it was passing, I failed to detect it with the microscope test; but in many of these cases the addition of a little fixed alkali or caustic lime with elevation of temperature to 98° secured its evolution. The normal amount of excretion by the urine of ammonia in combination as a salt, and the excess of such excretion in diseased conditions, are points on which, from deficiency of experimental evidence, I hesitate to speak.

In a paper read before the Royal Society, with a copy of which I have been favoured by the author, Dr. Bence Jones has endeavoured to show that, when salts of ammonia are administered internally, nitric acid in small quantities may be detected in the urine, a result due, as he opines, to oxidation of the nitrogen in the system. Lehmann has disputed this, on the ground that the mode of analysis pursued by Dr. Jones is calculated to mislead. Without entering into a discussion on this interesting topic, I would mention two facts. One is that, in an experiment where an animal was subjected to ammonia for a long time, until in fact death occurred, the