eases-their natural history, if I may say so;—a knowledge the importance of which cannot be over-estimated. Acute sthenic pneumonia has been shown to have a course almost as definite as the acute specific diseases; and to have an almost certainly favourable termination in youth.

The auscultatory signs of tubercular pneumonia are not to be distinguished from those of ordinary pneumonia; but the former as rarely spares the young as the latter kills them. The diagnosis between these two affections may be made absolutely by their course. The knowledge of the duration and course of diphtheria-the period at which the larynx is likely to become involved, albuminuria to occur, and the nervous phenomena to supervene, has given us great advantages in its treatment.

I may illustrate the folly of attempting to estimate the value of special treatment of a disease before the natural history of the disease is known, by the following facts.

In 1817-19 an epidemic of fever prevailed in Edinburgh. This epidemic met with a singularly able historician in Dr. Welche. His object was not to write a history of the epidemic, but to prove the great value of blood-letting in fever. Dr. Welche shows that the mortality from fever in Edinburgh before the employment of venesection was very great, the percentage of fatal cases was very considerable; and he proves indisputably that, after the introduction of free blood-letting, the mortality was comparatively, nay absolutely, trifling. So frequently did the fever cease after the blood-letting, so quickly did the cessation of the fever follow on the venesection, that to the

man who employed the lancet boldly in the treatment of fever Dr. Welche thought it might be said "O homo! jugulasti febrem.”

Now the investigations of the physicians of the past twenty-five years have proved that the disease which Dr. Welche supposed he had killed by blood-letting was a disease which runs a short and definite course, ends spontaneously on or about the date at which he thought he killed it by blood-letting, and terminates almost always. in health under all treatment and without treatment. It is wonderful to observe how few died, though in the hope of killing the fever 120 to 130 ounces of blood were taken from the arm in a few days in several cases.

Another great advance in practical Medicine is the recognition of the frequent relation of local lesions to chronic constitutional states. No practitioner would now think of treating a local disease till the diagnosis of the constitutional state had been made.

For example, in bronchitis in a child both the prognosis and the treatment will be greatly modified by the fact that the little one is the subject of tuberculosis, of strumosis, of rickets, or of constitutional syphilis. In Bright's disease both prognosis and treatment will be modified by the fact of the patient being the subject of constitutional gout, of tuberculosis, or of syphilis.

So in regard of intracranial diseases, I may instance meningitis, tumour, disease of arteries, interfering with nutrition as local diseases, for the successful treatment of which it is now admitted that a knowledge of the constitu

tional state is in every case essential. Surely this is a great stride in practical medicine.

The increased accuracy of late attained in the definition of special diseases and of their course has been greatly assisted by the use of special instruments for the detection of physical changes previously imperfectly recognisable. Without the microscope the existence of leukæmia could not have been established; to its aid is due the knowledge of the parasitic characters of tinea tonsurans, tinea favosa, chloasma, and thrush; it has yielded indisputable evidence of progressing destruction of lung-tissue; to it we are indebted for the separation of hydatid cysts from the various forms of simple cysts with which they were so long confounded, as well as for a knowledge of the real nature of the former. The diagnosis, prognosis, and treatment of Bright's disease are all aided by the information the micro

scope conveys.

The thermometer to the clinical physician affords, as we have already seen, information of the highest practical value, whether regard be had to diagnosis, to prognosis, or to treatment.

The laryngoscope has enabled us to appreciate changes in the larynx which, without its aid, could not have been suspected, and to determine with certainty the presence of other lesions which, without it, could only have been suspected, e.g. growths within the larynx, paralysis of one or both vocal cords, small ulcers on the cords; and in two of these affections, to detect the disease with certainty is to be able with equal certainty to cure the patient.

The ophthalmoscope has afforded valuable definite information in aid of the diagnosis of some of the most obscure diseases of the brain and its membranes.

The sphygmograph has accomplished something for medicine as a science and an art, and promises much

more.

The balance is an instrument of great importance in determining the progress, that is the advance or otherwise, of certain important diseases, and so the value of the treatment being pursued; e. g. diabetes and phthisis.

Another great gain to modern Medicine has resulted from the diffusion of more correct ideas as to the meaning of the word cure, and of the distinction to be drawn between curing the disease and curing the patient.

The meanings of the word cure are best illustrated by reference to some special diseases.

We cure scabies. It is to be observed however that when we cure scabies we do not cure the visible symptoms of the disease; but we destroy the agent, the presence of which calls forth the visible symptoms. That agent being destroyed, nature cures the inflammation, vesication, pustulation, &c. We do what the surgeon does when he removes a thorn; he does not cure the inflammation excited by the thorn, but he removes that which keeps up the inflammation; and then nature cures the inflammation.

Ague is, again, a disease of another kind, which we remove, that is, cure, by the use of certain drugs. The ague fit once established is not curable; i. e. it runs its

course; and then we prevent the recurrence of the aguefit. We cure or remove the condition which leads to the recurrence of the fit, over the symptoms and duration of which we exercise no control. We cure the disease.

Epilepsy is another disease which we cure. Each fit, like the attack of ague, once begun runs its course uncontrolled. Epilepsy is sometimes occasioned by a special exciting cause, an irritant present at some one point, the thorn so to say. For example, a man suffered from epilepsy, he passed joints of tape worm; the worm was removed, and the fits did not recur. Years afterwards the epilepsy recurred, and he said, "Oh! I must have another tape-worm." A dose of male-fern did remove another tape-worm; and again the fits ceased. Now we may say the epilepsy was cured by the removal of the tape-worm, but it is to be noted that, although the excitement of the attacks was removed, the disease of the nervous system was untouched, as was shown by the recurrence of the manifestations of the disease as soon as the special irritant was again applied.

Again, we cure epilepsy, we say, when by the administration of drugs we so modify the nervous system that, on the applications of the irritants which previously induced a fit, no attack follows.

We cure patients suffering from the acute specific diseases. An acute specific fever is analogous not to ague generally but to a single fit of ague, and as we have no drug that controls the duration of the fit, so we have no drug that controls the course or duration of the acute