4. Do not decide upon blood-letting, in difficult cases, until you have felt the pulse for some time. The Chinese physicians never prescribe until they have counted 49 strokes.
5. Feel the pulse at the intervals of four or five minutes, when you suspect that its force has been varied by any circumstance not connected with the disease, such as emotions of the mind, exercise, eating, drinking, and the like.
6. Feel the pulsations of the arteries in the temples and in the neck, when the pulse is depressed or imperceptible in the wrists.
7. Request silence in a sick room, and close your eyes, in feeling a pulse in difficult cases. By so doing, you will concentrate the sensations of your ears and eyes, in your fingers.
In judging of the states of the pulse which have been enumerated, it will be necessary always to remember the natural difference, in its frequency and force, in old people and children; also in the morning and evening, and in the sleeping and waking states of the system.
Much yet remains to be known upon this subject. I have mentioned the different states of the pulse, which call for bleeding, but it is more difficult to know when to prescribe it, when the pulse imparts no sign of disease. In general it may be remarked, where the disease is recent, the part affected important to life, and incapable of sustaining violent morbid action long, without danger of disorganization, where pain is great, and respiration difficult, the pulse may be disregarded in the use of the lancet.
But to return.
II. Regard should be had to the character of the reigning epidemic, in deciding upon blood-letting. If the prevailing fever be of a highly inflammatory nature, bleeding may be used with more safety, in cases where the indications of it from the pulse are somewhat doubtful. The character of a previous epidemic should likewise direct the use of the lancet. The pestilential fever which followed the plague in London, in 1665, Dr. Sydenham says, yielded only to blood-letting. It is equally necessary in all the febrile diseases which succeed malignant fevers.