( 326 ) 



L, will be more comprcfled than in the tube B, folely by reafon of 

 the gravitation of the liquor, if B is placed higher than F and L ; 

 but if the liquor in thefe fmall tubes has a paflage into other fmall 

 tubes, in which the liquor can riie to the height at Q, then the 

 preflure on the liquor will be the fame in all the other tubes ; for the 

 prefllire is the fame in every part of the tube as at its bafe, regard 

 being had to the diameter or breadth of thofe tubes. 



In a word, the current of the liquor will be of the fame fwift- 

 nefs in every one of thefe branches. 



Now, if we conlider the large tube, j^^. 4, A B C D E F, to be an 

 artery, and out of it various fmall arteries and their branches 

 arifmg, as B G, CH, D I, EK, and FL, and that MNOPQR 

 is a vein into which the arterial blood is difcharged, we mull necef- 

 farily fay that L M, K N, 10, HP, and G Q, are veins, becaufe 

 G H I K L are the places where the blood begins to take its courfe 

 backwards. 



But the circulation of the blood will be very much retarded in 

 the extreme parts of our bodies, when the limbs are cold ; whence 

 it comes to pafs that the blood-vellels in thofe parts are fo diftended 

 that our hands and feet are fwelled, and therefore there cannot be 

 fuppofed to be fo rapid a motion of the blood in the extremities, as 

 in thofe veflels which lie in the more internal parts of the body, 

 unlefs all the parts of the body are equally warm. 



A certain Dodlor of Phyfic, to whom, among other perfons, I had 

 fliewn the circulation of the blood, told me that this circulation 

 had alfo been exhibited to him by a chirurgical gentleman ; and on 

 my defiring to know how it was Ihewn to him, he faid by injeding 

 quickfilver into an artery, which circulated back again through a 

 vein ; but when I atked him how they were aflured that one of the 

 veflels in which the experiment was made was an arter}', and the 

 other a vein, he anfwered that they were not certain as to that 

 point. I alfo alked him what was the lize of the vein in which the 

 quickfilver, fo injeded, was circulated ; to which he anfwered, that 



