14 



THE BLOOD 



their own observations and those of preceding 

 generations, may then make considerable advances, 

 when many shall run to and fro, and knozvledge 

 shall be increased" 



His account of his plan of measuring the blood- 

 pressure, and of one of many experiments that he 

 made on it, is as follows : — 



" Finding but little satisfaction in what had 

 been attempted on this subject by Borellus and 

 others, I endeavoured, about twenty-five years 

 since, by proper experiments, to find what was the 

 real force of the blood in the crural arteries of dogs, 

 and about six years afterwards I repeated the like 

 experiments on two horses, and a fallow doe ; but 

 did not then pursue the matter any further, being 

 discouraged by the disagreeableness of anatomical 

 dissections. But having of late years found by- 

 experience the advantage of making use of the 

 statical way of investigation, not only in our 

 researches into the nature of vegetables, but also 

 in the chymical analysis of the air, I was induced 

 to hope for some success, if the same method of 

 enquiry were applied to animal bodies. . . . 



" Having laid open the left crural artery (of a 

 mare), I inserted into it a brass pipe whose bore 

 was \ of an inch in diameter ; and to that, by means 

 of another brass pipe which was fitly adapted to it, 

 I fixed a glass tube of nearly the same diameter, 

 which was 9 feet in length ; then, untying the 

 ligature on the artery, the blood rose in the tube 

 8 feet 3 inches perpendicular above the level of the 

 left ventricle of the heart, but it did not attain to 

 its full height at once : it rushed up gradually at 

 each pulse 12, 8, 6, 4, 2, and sometimes 1 inch. 



