CIRCULATION OF THE BLOOD. 115 



Thus, in phlebotomy, when the blood escapes forcibly and to a 

 distance, in a full stream, and from a large orifice, it is thicker, 

 has more body, and a darker colour ; but, if it flows from a 

 small orifice, and only drop by drop, as it usually does when 

 the bleeding fillet is untied, it is of a brighter hue; for then 

 it is strained as it were, and the thinner and more penetrating 

 portion only escapes; in the same way, in the bleeding from 

 the nose, in that which takes place from a leech-bite, or from 

 scarifications, or in any other way by diapedesis or transuda- 

 tion, the blood is always seen to have a brighter cast, because 

 the thickness and firmness of the coats of the arteries render 

 the outlet or outlets smaller, and less disposed to yield a ready 

 passage to the outpouring blood; it happens also that when 

 fat persons, are let blood, the orifice of the vein is apt to be 

 compressed by the subcutaneous fat, by which the blood is 

 made to appear thinner, more florid, and in some sort arte- 

 rious. On the other hand, the blood that flows into a basin 

 from a large artery freely divided, will look venous. The blood 

 in the lungs is of a much more florid colour than it is in the 

 arteries, and we know how it is strained through the pulmonary 

 tissue. 



2d. The emptiness of the arteries in the dead body, which pro- 

 bably misled Erasistratus in supposing that they only contained 

 aereal spirits, is caused by this, that when respiration ceases the 

 lungs collapse, and then the passages through them are closed j 

 the heart, however, continues for a time to contract upon the 

 blood, whence we find the left auricle more contracted, and the 

 corresponding ventricle, as well as the arteries at large, appearing 

 empty, simply because there is no supply of blood flowing round 

 to fill them. In cases, however, in which the heart has ceased 

 to pulsate and the lungs to afford a passage to the blood simul- 

 taneously, as in those who have died from drowning or syncope, 

 or who die suddenly, you will find the arteries, as well as the 

 veins, full of blood. 



3d. With reference to the third point, or that of the spirits, 

 it may be said that, as it is still a question what they are, 

 how extant in the body, of what consistency, whether separate 

 and distinct from the blood and solids, or mingled with these, 

 upon each and all of these points there are so many and such 

 conflicting opinions, that it is not wonderful that the spirits, 



