Refpiration , and the Ufe of the Blood . 231 
intimates their abounding with fulphur, which makes 
i t them more fufceptible and retentive of heat than thofe 
bodies which have lefs of it. 
He alfo fuppofes, p. 102, that another great ufe of the 
lungs is to attenuate and feparate the globules of blood ; 
and that the floridnefs of the arterial blood above the ve- 
rnal may, in a good meafure, be owing to the ftrong agita- 
ition, friction, and comminution, which it undergoes in 
palling through them. In like manner, in an experiment 
which he made for the purpofe, blood much agitated in a 
iclofe glafs veffel was obferved to be very florid, not only 
| ion its lurface, but through its whole fubftance, as arterial 
Iblood is, vol. II. p. 1 o 2. I would obferve, however, that 
| iin this expement, the blood mull have acquired its florid 
(Colour from the air with which it was agitated. 
He adds, that it is probable, that the blood may, in the 
lungs, receive fome other important influence from the 
air, which is in fuch great quantities infpired into them. 
In other places, however, he explodes the dodlrine of a 
vivifying fpirit in the air. It has long, he fays, been the 
{ fubjedl of inquiry to many, to find of what ufe it is in 
refpiration; which, though it may in fome refpedls be 
known, yet it muft be confefTed, that we are Hill much 
in the dark about it, vol. II. p. 102. 
Suffocation, he fays, vol. II. p. 27 1 . confilts chiefly in 
the falling flat of the lungs, occafioned by the grolihels 
of the particles of a thick noxious air, they being, in that 
floating Hate, moll eafily attracted by each other, as we find 
that fulphur, and the elallic repelling particles of air are ; 
