T 



•v.. 



taki 



romth 



eoth 



e 



er 



proper 



c 



r 



inch 

 of 



out 

 vena 



for the 



animals 



irft, that 



ough the 



e veins 



ly; both 



relive ar- 



an 



1 



d roots 

 bforbent 



irk, with 

 •oot-ftalk 

 iiiiDences 



d venous 

 oftbc 



ce 



3; an 



dis 



n 



der i'ur- 

 ood froi» 



he blood 



ex at tl^^ 

 unk 



tr 



to 



t' 



ena 



cava 



be 



|icn5t 



Sect. V 



3- 



AND VEINS 



d 



and returns to the caudex of the bud 



and to the foot-ftalk of the leaf. 

 3. The power, which prod 



circulation with 



h 



o-etables, a£ts with an aftonifhing force 



In fome of the experi 



meats of Dr. Hales, who fixed glafs tubes to vine-flumps in the fp 



the fap-juice rofe above thirty feet 

 bly arife flill high 



d in fom 



muft proba 



I 



th 



vernal months before th 



pended j and this either folely by the adivity of the abforbent mouth 



of thefe veflel 



or 



ffifted by th 



a 



of th 



fid 



t 



which appear to confift of a fpiral line,' as defcribed in Sed. II. 7. of 



this work. 



When the fap-juice rifes thirty-five feet high, which is about the 



weight of the atmofphere, the column prefTes about fourteen pounds 



Now if the area of the mouth of an abforbent 



on every fquare inch 

 veflel be only one ten thoufandth part of the area of a fquare inch, the 

 ten thoufandth part of fourteen pounds is the whole that countera6ls 

 the efforts of each abforbent mouth; and as the veflTels of vegetables 

 appear to have both very rninute diameters, and very rigid fides, they 

 are thence prevented from aneurifm or rupture by the prefTure of fo 

 high a column of fap-j 



^ 



The fame philofopher, by fixing glafs tubes to the arteries of horfes, 

 as near the heart as was prafticable, found the blood in them to rife 

 only nine or ten feet ; whence it appears, that a circulation of blood 

 may be carried on more forcibly by the adion of the mouths of ab- 

 forbent veflels, than by the apparently more violent exertions of the 

 heart, the power of which was calculated by BoreUi and others to be 

 fo enormoufly great, as to equal the prelTure of fome thoufand pounds, 

 as the counter preffure of the moving blood a£ls on fo large a furface 



one 



as that of the whole internal fides of the heart. 



But as a column of blood nine feet high prefixes with lefs than 

 third of the weight of the atmofphere, or about four pounds on every 

 fquare inch of furface ; and as the internal furface of the left cavity 



of 



