rj 
Dr. Priestley’s Obfervations on 
air as of any other ufe than to put the lungs in motion, 
think, that heat is produced in the lungs by the attrition 
of the blood in palling through them .Mifc. T'aurin. vol. 
V. p. 36. The red colour of the blood has been thought 
by fome to be caufed by this attrition in the lungs ; but 
lower refuted this notion, chiefly by obferving, that the 
attrition of the blood is greater in the mufcles, from 
which, however, it always returns black, Ibid. vol. I. p. 7 4. 
Dr. whytt thought there was fomething of a vital 
and flimulating nature derived from the air into the 
blood, by means of which it made the heart to contrail, 
HALLER, vol. III. p. 336. 
boerhaave fays, that air not changed is deadly; not 
on account of heat, rarefaction, or denfity, but for fome 
other occult caufe. Mifc. Taurin. vol. V. p. 30. 
Dr. hales, who has thrown much more light upon 
the doCtrine of air than all his predeceffors, was equally 
ignorant of the ufe of it in refpiration; and at different 
times feems to have adopted different opinions concern- 
ing it. 
In his Statical EJfays , vol. II. p. 321. he fuppofes, that 
air is rendered alcaline by breathing, and corrected, in 
fome meafure, by the fumes of vinegar. 
In agreement, as he obferves, with boerhaave, he fays, 
p. 100. that the blood acquires its warmth chiefly in the 
lungs, where it moves with much greater rapidity than in 
any other capillary veffels of the body, vol. II. p. 87; 
but that one ufe of the air is to cool the blood, p. 94 ; and 
he makes an eftimate of the degree of this refrigeration. 
The red colour of the globules of blood, he fays, p. 88, 
intimates 
