Organs of the

brain awake

in succession.

Macnish.

sleep the efnished quantity of arterial blood in the

fect of a dimi

sleep, changes of a perfectly opposite character take place on the approach of the waking state-changes which have been already shown to increase the vigour of the heart. The mus- See page 50. cular system, which, during sleep, had been in a state of complete repose, is now thrown into action, the position of the trunk of the body is changed, and the limbs are stretched. In like manner as, when on the approach of sleep, one organ of the brain slumbers after another, so on waking one organ is awoke after another, a certain time being required before all the intellectual powers are revived; and if we are awoke very suddenly out of a profound sleep, Your ideas are exceedingly confused, and it is some time before we can be made to comprehend what is said to us." As all the phenomena which precede sleep must, it is evident, materially contribute to equalise the supply of the vital fluid to every organ, and to every part of the body, they must undoubtedly have also the effect of diminishing, in a special manner, the supply of the systemic blood to the brain; and, consequently, the various modifications both of sleep and wakefulness can be most satisfactorily explained by contemplating the corresponding changes which take place in the velocity of the currents of the blood in the cerebro-spinal system. Likewise, as all these modifications of sleep must depend upon changes in the action of the central organ of the circulation, so will each of them become important signs of the state of the heart, both in health and in disease. Indeed, I may here remark, that there are no morbid phenomena connected with the cerebro-spinal system which, when viewed conjointly with those manifested in the other systems of the economy, afford more unequivocal symptoms in disorders of the heart than the various modifications of sleep.

The account which I have now given of the nature of sleep meets with an additional confirmation by reviewing those causes which disturb or altogether prevent sleep, and, likewise, those by which it is promoted.

The means which are usually resorted to for preventing sleep, such as drinking tea or coffee, increase the heart's

brain;

its modifica

tions are im

portant

symptoms.

Sleep-how

disturbed or

promoted.

Causes of stupor.

The sleep of disease.

action, and will, consequently, increase the supply of arterial blood to the brain: whilst those which are employed to promote sleep are such as tend to subdue the action of the heart, and thus diminish the quantity of arterial blood which is sent to the head. The practice of immersing the feet in warm water, to which has been added a stimulating ingredient, as vinegar, mustard, or common salt, disposes to sleep by diminishing the quantity of blood within the head, and thus increasing the supply to the extremities. Sponging the body with diluted vinegar, spirits, or salt water, by producing a glow on the skin, also relieves the internal organs of a certain quantity of blood; and taking fluids into the stomach likewise disposes to sleep by diverting blood to that organ.

When the intellectual powers have been kept in a state of excitement, the heart's action is often so much increased that sleep is interrupted, if not altogether prevented, and, therefore, instead of endeavouring to sleep immediately after any active mental employment, if the body be kept for a while in a state of repose, the excited vascular system will be calmed and tranquillised. This effect of mental excitement is remarkable even in children, for it may be observed that when a child falls asleep immediately after any unusual excitement, its sleep is generally disturbed and unrefreshing. The judicious nurse, therefore, allows the excited system to be tranquillised before she permits the child to fall asleep.

Contrasted with watchfulness or disturbed sleep, is stupor or an unnatural disposition to sleep a state caused by a very different condition of the circulation in the brain to that which has just been described. In place of an increased supply of arterial blood-the cause of intellectual excitement -there is, in stupor, a congestion of venous blood within the head, a state wherein the veins are preternaturally distended, analogous to the congestion so frequently occurring in the veins of other orgaus, particularly those of the abdominal viscera.

Sleep is also liable to other disturbed conditions, most of which appear to depend either directly or indirectly on the state of the circulation in the brain, the phenomena of which

are, however, very different from the excitement caused by an increased supply of arterial blood, or from the stupor produced by venous congestion.

After describing the sleep of health, an elegant writer reverses the picture and paints with his finished pencil the sleep of disease. "It is short, feverish, and unrefreshing, disturbed by frightful or melancholy dreams. The pulse is agitated, and, from nervous excitation, there are frequent startings and twitchings of the muscles, nightmare pressing like an incarnation of misery upon the frame. Imagination, distempered by its connection with physical disorder, ranging along the gloomy confines of terror, holding communication with hell and the grave, and throwing a discolouring shade over human life."

Like other functions of the economy, sleep may, therefore, be either natural or diseased, and, as various changes to which it is liable may be accounted for by changes in the circulation, the different conditions which it presents will afford, as has been already said, important signs in many diseases of the heart-irregularities in the venous circulation within the head being referable to those of the right, and alterations in the arterial circulation indicating changes in the left, heart.

Macuish.

THE

DISEASES OF THE HEART.

CHAPTER V.

OF THE DISEASES OF THE HEART IN GENERAL.

Arrangement of the subject; the pathological doctrines established by induction; phenomena of the healthy circulation; importance of a knowledge of healthy structure; utility of an inquiry into the functional diseases of the heart; frequency of diseases of the heart; state of the heart's pulse long neglected by pathologists; attention paid to it by the Chinese.

of the sub

BEFORE entering upon the consideration of the particular Arrangement diseases of the heart, I propose to give a general view of ject. their various phenomena, of the causes which produce them, of the symptoms by which they are accompanied, of the principles on which their treatment should be conducted, and of their classification.

By adopting this plan it has appeared to me that the materials which I have gathered together may be greatly condensed, and that endless repetitions will be prevented,repetitions which would have been unavoidable had I attempted, when treating of each disease, to enter into every minute detail; whereas, by first giving a general view of the nature of all the diseases of the heart, and of the means best adapted for their treatment, such observations will be found applicable to its particular maladies. Thus, instead of being obliged to repeat, when treating of each disease, those