ON THOUGHT IN MEMCINE. 211 



only acquainted with alterations in mixture. The four 

 cardinal fluids, representatives of the classical four 

 elements, blood, phlegm, black and yellow gall ; with 

 others, the acrimonies or dyscrasies, which had to be 

 expelled by sweating and purging ; in the beginning of 

 our modern epoch, the acids and alkalies or the alchy- 

 mistic spirits, and the occult qualities of the substances 

 assimilated all these were the elements of this chem- 

 istry. Along with these were found all kinds of phy- 

 siological conceptions, some of which contained remark- 

 able foreshadowings, such as the sjufrvrov 0e/?/*oz/, *the 

 inherent vital force of Hippokrates, which is kept up 

 by nutritive substances, this again boils in the stomach 

 and is the source of all motion ; here the thread is 

 begun to be spun which subsequently led a physician 

 to the law of the conservation of force. On the other 

 hand, the irvsv/Aa, which is half spirit and half air, 

 which can be driven from the lungs into the arteries 

 and fills them, has produced much confusion. The 

 fact that air is generally found in the arteries of 

 dead bodies, which indeed only penetrates in the 

 moment in which the vessels are cut, led the ancients 

 to the belief that air is also present in the arteries 

 during life. The veins only remained then in which 

 blood could circulate. It was believed to be formed 

 in the liver, to move from there to the heart, and 

 through the veins to the organs. Any careful ob- 



