Of the Circulation of the Blood. 3 
other, and feveral of them will be divided into the final- 
ler ones of which they are compofed. 
By either of thefe methods, the globules of the blood 
may be diftindily feen, and a little pradtice will difcover 
any alteration that may happen in the colour, fhape, or 
fize of them; in its feveral changes between ficknefs 
and health. Mixtures of medicinal, or poifonous liquors, 
may be blended with it immediately as it comes from the 
vein, and a drop of this mixture, if applied as before 
directed to the microfcope, will difcover what alterations 
can be produced on the contexture of the blood. The 
vefTel in which the blood is received, fhould be put into 
a bafon of water, fomewhat hotter than the blood b , to 
prevent its coagulating before the mixture. 
The circulation of the blood through its vefTels, is to 
be feen in fuch fmall creatures, whofe tranfparency per¬ 
mits us to look within them, or in the thitinefl parts of 
larger ones; by which we are very well informed, the 
whole animal fyftem being eftablifhed on the fame plan, 
the circulations carried on in vefTels of a like form, both ' 
in the mean eft and nobleft living creature, and accele¬ 
rated or retarded by the fame caufes. 
In thefe fmall creatures we are not only able to fee 
the general courfe of the blood, but can perfectly diflin- 
guifh each globule, and the alteration they fuffer in 
palling out of the larger into the more minute vefTels, 
many of them being fo fmall, that fmgle globules can 
icarce enter, till they are compreffed into an oval form j 
and yet thefe very vdTels are large, when compared with, 
the fmeft of all, in which the globules muff be divided 
B 2 and 
b The exaft blood-heat of the water, may be obtained by a 
pocket thermometer, made with quickfslver, with which the 
reader may be fupplied at my fhop, at Tycho Brahe’s Head in 
Fleet-Street, No. 60. 
