and its frequent diffusion under a virulent epidemic form would all seem to require a description more precise than any which have been quoted from antiquity. Admitting the account of Rhazes as the first that has any certain application to the disease, it is undoubtedly difficult to conceive why it should then have appeared in this part of the world for the first time. Yet is the fact not really more obscure than many other points in the history of these contagious epidemics. Their original generation among mankind is the great mystery of the case, to which all others are subordinate; and for this, as far as we can see, no source of solution is ever likely to be afforded us.

Reviewing the whole of this inquiry, the following inferences, whatever their respective truth or probability, may be admitted as giving a more distinct form to the various arguments it involves.*

*

First, That the series of actions or changes, constituting these diseases, have their seat in the blood, and are carried on throughout by the circulation.

Secondly, That, although we have no cognizance of the actual physical state or changes which give protection against

* In stating these conclusions I still refer chiefly to the three great diseases of this class. The difficulty has already been mentioned of giving the hooping-cough any common place with them, even under admission of its infectious nature, and of the peculiar character which the title of the chapter conveys. The fact of exemption from a second occurrence of the disorder is indeed much more doubtful in this case; and what appears such, may be often merely the effect of different time of life in altering the liability to the morbid cause; or giving it direction to other parts of the body, and thereby changing the whole aspect of the symptoms. The latter view, under a more general application, has been repeatedly noticed, as sanctioned by various facts, and leading to many curious inferences.

their occurrence or recurrence, there is more reason for seeking these in an altered state of the blood than in any other part of the animal organization.

Thirdly, That the conditions which render one disease incompatible with another- or produce the various results of their mutual interference or limit to man their production and developement—all probably depend on the same physical principles as the simpler fact of immunity, and have equally their source and seat in the blood.

Fourthly, That the state of immunity, on whatever bodily conditions it depends, is liable to fluctuation in various ways; is often partial and imperfect when first obtained— occasionally diminished or lost by time, even where there is presumption of its having been most complete at firstpossibly affected in some degree, and after a certain lapse of time, in all; the rate of such changes being different in different persons, and modified also by the access of other diseases, or by the contingencies of life.

Fifthly, That a constitutional or hereditary tendency exists throughout all these phenomena; -modifying susceptibility - determining, in conjunction with other causes, the regular or irregular course of the disease-affecting its degree of virulence- and giving liability to its recurrence: and that this habit of body is not limited to families, but extends even to larger communities.

Sixthly, That the several modifications, above named, depend further on the quality or quantity of the virus received in each case; -conditions admitting of being infinitely varied; and giving, in conjunction with the effects of season, locality, and human constitution, the peculiar character which every epidemic more or less assumes.

Other inferences might be specified; but the foregoing embrace all that are more important in the general view I

have taken of a subject, thus endless in its details, and in the hypotheses to which it has led. Though speculative in several points (an inevitable result of their nature), yet will they be found applicable in various ways, not merely to the theory of disease, but equally so to some of the most difficult and interesting questions which come under our consideration in practice.

EE

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CHAP. XXV.

ON THE USE OF OPIATES.

THE manner of employing opium in modern practice might, until very lately, have been cited among the many examples of perverse changes of fashion as to particular remedies and methods of treatment. All that tended to increase the credit and use of purgative medicines lessened for a time, in the same ratio, the reputation and employment of this remedy. A contradiction was presumed, greater than actually exists, between the two modes of treatment. The fear of confining the bowels and checking the secretions, constantly present to the mind of the practitioner, readily imbued the patient with the same alarm. And thus was prevented the adequate use of a medicine, having power of mitigating pain, of relieving spasm, of procuring sleep, of producing perspiration, and occasionally even of aiding the natural action of the bowels, by obviating the disordered actions which interfere with it.

I speak of this as having been, because it is certain that opiates are again more largely employed, since the introduction of morphia, as a common preparation, has furnished new methods of administering the remedy, and revived attention to the principles of its action. Yet even now it may be affirmed that there exists a distrust both as to the frequency and extent of its use, not warranted by facts, and injurious in various ways to our success in the treatment of disease. This is the more singular, seeing the boldness of our practice in other points; that we have in the sleep produced a sort of

limit and safeguard to its effects; and that we possess remedies of easy application for all injurious symptoms that can arise. To the insufficiency indeed of the quantities given, may be attributed in some part the comparative disregard into which the remedy fell during a certain period. Half a dose might disturb and distress the night which a full dose would have made one of perfect rest; or perplex the aspect of symptoms which a larger quantity would have alleviated or removed.

*

Yet medical experience does but follow common observation in recognising the inestimable value of sleep in sickness; of the suspension of pain, and the check to all disordered actions, thereby obtained. For pain and sleeplessness, though strictly but symptoms of other ailment, may often in practice be viewed as disorders in themselves, the removal of which is essential to the success of our general treatment. How frequently do we see a nervous restlessness come over the patient, the consequence of protracted sickness or other causes-retarding cure, by preventing the due effect of remedies, and receiving no relief itself from the means employed for the disease. In such cases the physician is not to submit himself to names or technicalities. The regular course of treatment must be suspended till the hinderance is removed; and even seeming contradictions to this course may safely be admitted for the attainment of the object. Here opium is the most certain and powerful of the aids we possess; and its use is not to be measured timidly by tables of doses, but by fulfilment of the purpose for which it is given. A repetition of small quantities will often fail,

* A physician of large practice, whom I knew but in the latter days of his life, acted not unwisely, perhaps warily, in carrying about with him a box of small opium pills; with which he often gave relief, or made preparation for it, while yet in the house of his patient.