other and less violent diseases, we are led to calculate on the relation between the blood and the correct performance of the digestive function; but in cholera it is the sudden and rapid deterioration of the entire mass of vital fluid from the admission of a powerful poison from without.

You must ever keep in mind, dear Sir, the fundamental doctrine that organic nervous power is the primary agent of life and health. That secondary to this, for the same purposes, are the functions of digestion, blood-making, and nutrition. Remember, also, the circle of influences, and that any cause of disease which acts on any one part of that circle must soon affect the whole, through the close connection existing between them. They act and reäct on each other. Keep in mind, that from the blood are formed all the tissues of the body: thus you perceive how the tissue of the organic nerves themselves must share in the effects of all the causes which influence blood-making at any stage of the process.

In this way, you perceive, the primary agent of life and health, namely, the organic nerves, may be variously affected in their structure and material. Understand me, that their component nervous matter may be variously altered in their change of tissue, according to the cause affecting it. Thus we can account in some measure for the great variety of nervous disorders, and especially of those directly associated with diseases of the digestive organs. In this way we may account for the many strange fancies and feelings of the dyspeptic and hypochondriacal invalid. This point of nervous derangement through the deranged structure of the nerves, that is, their mal-nutrition, has in it much more than can be understood and explained. Equally incomprehensible is the mode of action of the causes of many malignant diseases which are of hereditary character; such as cancer and its numerous modifications, which I need not specify to you. There is scrofula also, with a numerous class of morbid conditions or disorders of the human system which are termed in technical language peculiar and morbid idiosyncrasies. Whatever may be the original cause of such conditions, you must regard them as constitutional, and as associated with morbid

assimilation of food, and a morbid state of the blood, and a morbid change of tissue. You must perceive, that with these conditions we must necessarily include the morbid state of organic nervous matter, which may stand in relation to the others as both cause and effect. It is in the circle of influences.

Moreover, you must recollect that the same cause of malnutrition, or morbid change of tissue, must also affect the brain and nerves of animal life, and give rise to some, at least, of the many kinds of mental aberration or insanity. Thus you perceive how intimate and important is the connection between the functions of digestion, blood-making, and nutrition, and the energy and permanent power of the mental faculties. Surely, you now see a sufficient and physiological reason for my earnestness in advising literary men, and especially ministers of the glorious Gospel, to give constant attention to the means of a healthy performance of these important functions. The means I allude to are comprised chiefly in diet and exercise: as a brief rule, spare diet and plenty of exercise. These, of course, are to be regulated according to the various requirements of each individual.

I often think of the cases of such men as the excellent Dr Watts. With all his gigantic power of intellect and excellence of Christian character, he proceeded in a course contrary to the laws of his physical constitution. He kept in close confinement to his studies, in the exercise of his mental powers, and in the neglect of diet and bodily exercise. He thereby became the victim of the strangest delusions respecting himself. He erred against the laws of organic life, and was overtaken by morbid organic impressions. The matter of his organic nerves became wrongly renewed, and wrong performance of their function was the natural result. Many very valuable years of his life were thus lost to himself and to the world.

It was otherwise, however, with the great John Wesley. You know that I am not a Wesleyan; yet I consider that John Wesley was a great man in the best sense of the word. With his innate shrewdness of intellect he became acquainted with the great fact respecting spare diet and plenty of exercise;

and through this knowledge he was enabled to preach and to travel until a very advanced age. He retained the vigour of manhood beyond the allotted age of man, three score years and ten.

Be assured that this great bearing of the secondary agent of life and health has greatly to do, through its derangement, in the causation and continuance of many diseases; but my limited space does not permit me to pursue the subject in its particulars.

However, I must take special notice of the other very momentous bearing of this secondary agent of the blood circulation, in causing its unequal distribution. You can easily conceive that the same derangement of the process of nutrition or renewal of tissue, which affects the nervous tissue, must also affect that of the blood vessels; and so it does. Because of this the blood vessels lose their wonted power of circulation; and, as a consequence, we have congestion of the veins, and the similar condition of the arteries constitutes inflammation. In all this you perceive the deterioration of the organic power, and the deteriorated quality of the blood. Hence there are congestions and inflammations of a specific nature, and amongst these you will have gout and rheumatism, which are of the number of these diseased conditions. In these you see clearly the true nature of disease, and an illustration of the doctrine that it is a process of the human body as natural as is that of health.

You see in these diseases a similarity without the sameness of operation as in malignant cholera. In this pestilence the organic power directs its efforts to the expulsion of a malignant poison from the body by vomiting and purging; whereas, in gout and in rheumatism the effort is for the removal of the less malignant matter of the disease, the materies morbi of technical language, from the internal and vital organs to the external parts; and principally to the joints, and to such parts as are composed of a like tissue to that of its internal seat.

The eruptive or exanthematous fevers of measles, small pox, and scarlet fever, afford us also striking examples of the agency of the curative force. In these diseases the secondary agents of life and health, the digestive and nutritive organs, are pri

marily affected; and as their functions are indispensable to life itself, the curative force is exerted to remove the morbid action from them to the external skin. This is seen to demonstration in the cure of these diseases. When the eruption is not properly developed on the surface of the body they very generally prove fatal. They kill by their action on the internal organs. So also do gout and rheumatism when they prove

fatal.

But I must now cut short this very interesting inquiry and investigation into particular diseases. Let me apprize you, however, that the same fundamental doctrine regarding the primary and secondary agents of health and disease is strictly correct in its application to all the conditions of the human body.

I intend to lead you to a just appreciation of the comparative efficiency of the different modes of cure which are advocated and practised in this country. I have already instructed you as to the true foundation of health, and disease, and its rational treatment. I intend to give you further illustration of these subjects, and more especially of the physiological principles laid down. Above all, I would lead you to a just appreciation of the primary agent, the organic nervous power.

LETTER VIII.

ORGANIC VITALITY OR NERVOUS POWER-ITS CONNECTION WITH HEALTH, DISEASE, AND TREATMENT-VIS MEDICATRIX NATURÆ--ILLUSTRATIONS OF ITS ACTION-FAVOURABLE STATE OF MIND FOR IT-UNFAVOURABLE STATE-JOHN WESLEY'S GREAT TRUTH-HUFELAND'S STATEMENTHAIR OF THE HEAD, AND CAUSES AFFECTING IT-MEDICINES AND THEIR TENDENCY OF ACTION, &c. &c.

MY DEAR SIR,

EVER welcome are your letters of inquiry, and I have much pleasure in giving you every information on the important subjects of our present very interesting correspondence. There is no point of human physiology which is of greater moment than that which is to be the chief subject of the three remaining letters I have yet to address to you. That subject is the organic vitality—the vis medicatrix naturæ, or curative power of nature-the vital force—the organic nervous power—the nervous energy—the curative force-the innate nervous energy. These various terms, and some others not specified here, are used by authors to signify the same thing. It matters not which one we adopt; indeed I shall use the terms indiscriminately.

I shall endeavour to explain to you, who are a non-medical reader, such particulars as I think the most necessary and important to be understood by you. I beg that you will give your earnest attention to what I bring before you: for the knowledge that I shall have imparted through these letters must prove of the greatest future service to you, and to every one who will carefully peruse them.

The organic nervous power, as I have already told you, is the primary agent of life and health; and you have to keep in mind that it is chiefly concerned in producing those unwonted conditions of the human system which constitute the symptoms of diseases, and by which they are usually named in the nosological language of our profession. Disease, I repeat, is a natural

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