Galen wrote three treatises on venesection, to which operation he was very partial. They are: _De venesectione adversus Erasistratum_; _de venesectione adversus Erasistrateos in Româ_; and _de curatione per venæ sectionem_. These works are deserving of great attention as containing many judicious observations and rules of practice, but which are delivered at so great length that we can scarcely venture even upon an abstract of them. His principles of treatment, however, are nearly the same as those of our author. He appears to have abstracted blood in great quantities. Thus he mentions having seen six lib. taken away in the course of a fever, and six heminæ at once in a case of hæmoptysis. Now the hemina being somewhat more than a half a pint, the quantity abstracted must have exceeded three pints. He strenuously inculcates that venesection proves useful by occasioning revulsion, and as a proof of this he instances the beneficial effects produced by opening a vein of the arm in cases of epistaxis. He practised bloodletting occasionally in cases of dropsy, as we have mentioned under that head. Bleeding from the arm he thinks prejudicial in cases of amenorrhœa, as it causes a determination of blood to the upper parts of the body, and, therefore, he directs us rather to bleed at the ankle. He agrees with Celsus that lean persons bear depletion better than such as are fat; and that venesection is not to be performed when there are undigested matters in the stomach. He states that persons in extreme heat or cold do not bear bleeding. He mentions that in bleeding from the basilic vein there is danger of wounding the artery, that a nerve lies under the median; but that the cephalic may be opened without danger.