PROP. VII.-That a first class of medicines, called HEMATICS, act while in the blood, which they influence. That their action is permanent.

1. That of these, some, called RESTORATIVES, act by supplying, or causing to be supplied, a material wanting, and may remain in the blood.

2. That others, called CATALYTICS, act so as to counteract a morbid material or process, and must pass out of the body.

Supposing that a medicine has fairly passed into the blood, and circulates round with it, there are now two ways in which it may behave itself.

In the first place, it may have a tendency towards some tissues or parts of the body, on which to exert its powers, as the nerves, or the glands, or muscular fibre, and may use the blood only as a vehicle by which most readily and easily to attain to these. Such are Neurotics, Astringents, and Eliminatives. They may not affect the blood, but they must pass through it.

But there is another and still more important class of medicines, whose action is particularly directed towards the blood itself. The blood, after their action, is different from what it was before. It may be a change for the better or for the worse; but there certainly is a change. Medical authors, with few exceptions, have been very backward to acknowledge the existence of medicines of this description. But even those who would fain have classed all medicines as stimulants or sedatives, differing only in the kind or degree of their action on the nervous system, have in many cases been obliged to confess that there is a set of remedies which they call Alteratives,' whose action, though slower, is more certain and more durable than that of the former. It is allowed that they alter the condition of the blood. To sup

se that they do so by first influencing the nerves, is to adopt a circuitous and uncalled-for explanation. It is proved that they pass into the blood. It is known that when actually applied to nerves, they do not affect them. From these considerations merely, without further evidence, it would seem tolerably clear that they act by influencing the blood itself, simply and solely. But this it will be my business to prove more at length directly.

Such medicines, then, I have designated Hæmatics, a simple and expressive term which has been used by others before me.

Considered as agents in the hands of the practical physician, Hæmaties may be said to differ from the three other classes of medicines in two important particulars. (1.) They act on the blood, and on the system generally. They therefore are of use to control or cure diseases, in which usually the system is at fault, and not a part of it only. But the others act on certain parts of the system, and are directed against certain conditions of those parts. They control symptoms. (2.) The medicinal action of Hæmatics is chiefly shown in morbid conditions of the blood, or system at large. It is not evidenced upon a healthy man. The only exception to this occurs in the case of Aliments, or articles of food, the first order of Restorative Hæmatics. And even this exception is rather apparent than real, for in fact Hunger and Decay must be considered as diseases, and food as medicine given to cure them. Hæmatics then do not evidence their proper action on a healthy man. But remedies of the three other classes, producing changes or affections of particular organs or parts of the body, and not absolutely requiring a diseased condition of the organ before such changes can be effected, do accordingly exert their action upon a healthy man. I have already alluded to this action on the healthy system as being named by most writers Physiological action. It is Therapeutical action, or operation. on a diseased system, which is most borne in view in my arrangement. It is altogether of most importance to us. For if we desire to cure disease, we must consider medicines as acting on disease. Having first discovered their therapeutical principle of action, then is our time to speak of their operation on the healthy body, and to inquire how far this working resembles or coincides with the former. And we shall then find, as I have just said, that the physiological and therapeutical actions of Haematics are different. Given to a healthy man, they are either inoperative or poisonous. That which in a small dose is remedium

to the sick, may have to be given in a large dose to be venenum to the healthy. Thus Acids and Alkalies, given in small doses to a healthy man, produce little or no effect; given in large doses, they cause wasting; whereas Arsenic, Mercury, and the Catalytics generally, are always more or less poisonous in a healthy system. But suppose the existence of certain diseased conditions, and the case is changed. The alkali is required to neutralize an abnormal acidity; and the Mercury counteracts in the blood the syphilitic poison. So that the therapeutical use of Hæmatics differs from their physiological action, inasmuch as it demands the pre-existence of some special condition of the system. But with the three other classes the case is different. Although their action is doubtless much modified by particular states of the organs, yet they act similarly on the nerves, muscular fibre, and glands, whether these are in a state of health, or the contrary. Opium will stupefy the brain, and Digitalis weaken the heart, as well in healthy as in diseased systems. The therapeutic use of Neurotics, Astringents, and Eliminatives, is not to counteract blood diseases, but local symptoms; to control morbid affections of the various organs, by their power to produce affections of an opposite character.

It is obviously necessary that a medicine of this class should be absorbed.

Now some of them tend in the end to act on the nerves or on the glands, not merely indirectly, but by bodily contact. But, whatever their subsequent action, they exert a primary and apparent influence on the blood itself. A little reflection will convince us that these remedies are more efficient than any others that can be selected out of the armoury of physic.

It is easy, and satisfactory for the time, to allay nervous excitement by employing a sedative, or by using a stimulant to communicate to the system a temporary strength. It is easy to knock down an inflammation, or to evacuate morbid humours, by stirring up the glands with a powerful eliminative. But these are all at the best but temporary measures. Unless the exigency be also of a temporary character, the disorder may soon return with unabated violence; again is the patient bowed down by its strong hand; again is the fatal termination seen looming in the distance but too distinctly.

Then has the physician to call to his aid more potent means, remedios of more permanent and certain efficacy. The disease is in the blood-ever circulating, breeding, and destroying. It is there that it must be met; let the physician strike boldly and warily there, if he would effect a cure.

These medicines, then, act in the blood. How they do so, and in what way they prove of use in the cure of disease, I shall next have to show, while attempting to prove the proposition in which I have briefly stated this mode of operation.

Hæmatics are very numerous, and very important: I shall thus devote some space to their consideration. But I must first lay down a broad distinction between the two divisions of Haematic medicines. The diseases in which they are used appear all to originate in the blood, however they may manifest themselves.

Now some of these diseases originate in a want of some principle or constituent of the blood, which want causes an aberration of the vital functions.

Thus, in anæmia, there is a deficiency of the Hæmatosin d the Sood corpuscles. In simple debility a want of a similar mature probably exists. In rheumatic fever and other disortxers an excess of acid is formed and eliminated, possibly from a the alkali by which it should be neutralized. In

lammatory fever there is an abnormal oxidation itie reinaceous compounds, possibly arising, as we shall

senin (2*, from a failure of some principles which are the

de oxygen. In diseases causing urinary deSavant of those principles which should natuIn typhoid fever there is said

as mater, and a deficiency of acid, in the s there is a deficiency of fat in erge malignant cholera there acies in the blood. Some sup

pose that in scurvy there is a want of the salts of Potash in the blood.

These diseases then, in some of which the want is proved, in others partly hypothetical, may be treated by medicines which supply the deficient matter, and thus restore a right state of things. They may supply it to the blood directly, or else cause it to be generated there. The former of these modes of restoration seems to be the most frequent, and may possibly, when we shall know more of such matters, be found to occur in all cases. This division of Hæmatics I have named Restoratives (Restaurantia). Their action, as we shall see, is in some cases apparent, in others more obscure. They restore the blood directly to its proper condition, if there is only a deficiency, but they do not in general seem to have the power of counteracting any morbid or active material that may exist in the blood. Nor do they, except in large doses, exert themselves any peculiar action on that fluid. In these respects they differ from the other division of Hæmatics. They also differ in another important character. Each Restorative has in healthy blood a substance analogous to or identical with itself: it replaces this when deficient.

Not so with other Hæmatics. There is in general nothing in the blood corresponding to them-or if there be in some cases, they are not introduced with the intention of supplying its want. Thus Restoratives may remain in the system, and are intended so to do; but these may not remain. They must pass out. In so doing they come under the head of Eliminatives, or that of Astringents. This is their secondary action, distinct from their primary and most important operation. What then is the curative action of these remedies?

A large class of diseases depends on the presence in the blood of a morbid material, or, what amounts to the same thing, on the constant working of a morbid process in that fluid. Some of these, as the eruptive fevers, will run a certain