Contents xiii 



aerial particles, p. 99. The vapour given off from fermenting' 

 substances does not seem to be air, p. 100. How inspired 

 air loses its elastic force, p. loi. On the use of the inspired 

 spirit, p. loi. The fermentation of the blood is produced by 

 it, p. loi. The blood is compared to the soil of a field, p, 

 102. Why arterial blood is brighter and redder than venous^ 

 p. 102. The heat of the blood depends on the inspired air^ 

 p. 104. Why animals become so hot in violent exercise, p. 

 105. Answers to various objections to what has been said, 

 p. 105. Contrary salts do not seem to effervesce more in a 

 vacuum than in open air, p. 106. When mixed together in a 

 vacuum they do not become so hot as otherwise, p. 107, 

 " The vital flame" and the "anima lucida" of Dr Willis dis- 

 cussed, p. 108. Whence fevers arise, p. 109. How the mass 

 of the blood degenerates into an acid liquid, p. no. It is 

 imbued with an acid-saline salt, p. no. Urine is also- 

 impregnated with such a salt, p. no. On other uses of the 

 inspired air, p. no. 



CHAPTER IX. — Whether Air can be Generated- 



Anew. 



An experiment in which air seems to be produced, p. in. 

 How we can ascertain how much elastic force any particular 

 kind of air possesses, p. 113. The vapour produced in the 

 way described tends to expand exactly like common air, p. 

 115. And yet it does not seem to be air, p. 116. Because it 

 is not fit to support life, p. 117. 



CHAPTER X.— How Fire is Propagated. Also, whv 

 Flame rises to a Point. 



Natural operations are carried on by means of very small 

 things, p. 120. Ignited particles are agitated with an elastic 

 impulse, p. 120. Natural fermentations are excited by the 

 blow of subtle matter, p. 121. Fire is the greatest fermenta- 

 tion, p. 122. Why every flame ends in a sharp point, p. 122. 

 Why a flame about to go out is last seen at the top of the 

 wick, p. 123. Why a flame once kindled does not continue 

 to burn, p. 123. The sulphureous particles are volatilised in. 

 the flame, p. 124. What soot is, p. 124. 



