Many cases, like the above, have come under my observation and immediate attention, and suffice it to say, I have never failed to ameliorate the condition of every individual that has applied to me, who was suffering under chronic affections, if they would follow my prescriptions--unless the system was incapable of reaction. Yours, truly, N. J. KNIGHT. LETTER V.--FROM DR. LESTER KEEP. FAIR HAVEN, Jan. 22, 1838. DEAR SIR,--Agreeably to your request, I will inform you that from September, 1834, to June, 1836, I used no meat at all, except occasionally in my intercourse with society, I used a little to avoid attracting notice. When I commenced my studies, life was burdensome. I knew not, for months, and I may say years, what enjoyment comfortable health affords. In a great many ways I can now see that I very greatly erred in my course of living. I am surprised that the system will hold out in its powers during so long a process in the use of what I should now consider the means best calculated to break it down. I cannot now particularize. But in college, and during my professional studies, and since, during six or eight years of practice in an arduous profession, I have been greatly guilty, and neglected those means best calculated to promote and preserve health; and used those means best fitted to destroy it. The summers of 1832, 1833, and 1834, were pretty much lost, from wretched health. I was growing worse every year, and no medicines that I could prepare for myself, or that were prescribed by various brother physicians, had any thing more than a temporary effect to relieve me. All of the year 1834, until September, I used opium for relief; and I used three and four grains of sulphate of morphine per day, equal to about sixteen grains of opium. Spirit, wine, and ale I had tried, and journeys through many portions of the State of Maine, with the hope that a more northern climate would invigorate and restore a system that I feared was broken down forever, and that at the age of thirty-seven. But, without further preamble, I will say, I omitted at once and entirely the use of tea, coffee, meat, butter, grease of all sorts, cakes, pies, etc., wine, cider, spirits, opium (which I feared I must use as long as I lived), and tobacco, the use of which I learned in college. Of course, from so sudden and so great a change, a most horrid condition must ensue for many days, for the relief of which I used the warm bath at first several times a day. I had set no time to omit these articles, and made no resolutions, except to give this course a trial, to find out whether I had many native powers of system left, and what was their character and condition when unaffected by the list of agents mentioned.