When we consider the admirably curious structure of the human mechanism, it must clearly appear, how easily the animal œconomy may become disordered. But so kind has the ALLWISE AUTHOR of our existence been to his creatures, that on the slightest indisposition, the whole system is sensible of the least disagreeable sensation; and every part, with a social and sympathetic friendship, is ready to relieve the fabric from whatever is obnoxious, and causes the disturbance. As nothing has a greater share in life than the blood, so nothing likewise on the least indisposition, is sooner set in commotion, and gives the alarm, than this very liquor, in which life itself is contained; and the circulation of this fluid in the arteries, furnishes us with the greatest prognostic, namely, the _pulse_, by which we may, with any degree of certainty, judge of the state of the body, and foretell good or bad events. How beneficial it is then to be acquainted with this knowledge, I shall leave to every rational being to determine. Every artery in the living body constitutes a _pulse_, as has been explained in Sect. V. in the foregoing lecture. And it is demonstrative from simple reason, that the pulsation of such arteries must be in proportion to their magnitude, greatest in the heart, whence they take their origin; till the vibration must gradually be lost to the touch, as they become insensibly small, and lose themselves in their ramificatory capillary tubes. The artery which is most convenient to our examination, is that which lays immediately to the touch on our wrist, below the thumb, on the radius, just below the knuckle of that bone; and it is there we are best able to distinguish the pulsation of the arteries, as being most exposed to the external touch; because it is immediately between the skin and the flat of that bone. Thus much premised, we will first consider the _pulse_ in the sound state; and next make a comparison with that in people labouring under diseases. In a full grown man, in the vigour of health, the pulse ordinarily beats once to every second, that is, 60 times in a minute, 3600 in an hour, and 31,536,000 times in a year. It varies however in different subjects, according to the stature, temperament, condition, time, and action of the same; insomuch, that two persons equally in a good state of health, shall, however, differ widely in their pulses. Yet, notwithstanding, there are peculiar signs, which will ever make a true distinction between health and sickness; practice however is requisite to form a proper judgment of such distinction. In order to lay a proper foundation to understand the nature of this great prognostic, I shall divide the pulse into the following classes: