VOL. XVII.] PHILOSOPHICAL TRAKS ACTIONS. 583 



ture of veins, arteries, nerves, lympheducts, &c. but we shall find the great 

 bulk of them to be vesicular ; which seems to me to be a continuation of the 

 wind-pipe, divided and subdivided into many branches, and these still spun out 

 into smaller and smaller pipes, all of them hollow ; and the farther they run, 

 the thinner their sides grow, which upon the inspiration of air swell and grow 

 round, and upon expiration become flaccid, and abate something of that figure. 

 That these pipes should run to a great length hollow, though very small, I the 

 less wonder at, having seen a hollow pipe of glass drawn out at the flame of a 

 lamp so very small, as to be scarcely visible without a microscope, and yet was 

 so hollow as to take up tinged spirit of wine. The sanguiferous vessels are 

 divaricated through all the lobes of the lungs, and very closely accompany -each 

 vesicula, in order to receive some considerable benefit from it ; and this appears 

 to the eye ; for in an instant a dark and foul blood is changed into a bright 

 florid red colour. Thus the very structure of the lungs, the change of colour 

 both in the blood and in our experiment, the one from a dark opaque colour to 

 a noble scarlet, the other from a pale or colourless liquor to a rich ultramarine 

 blue, all show that this alteration is owing to the air. Nor is the air thus in- 

 fused into the lungs for a bare colour, and of no farther use ; but I am apt to 

 believe the great fermentations of the blood, the cause of the motions and 

 actions of the muscles, the animal spirits themselves, the great spring of mo- 

 tions, derive their energy and powers, if not nature, from hence.* 



Corollary 1 . — ^The air abounds in volatile salts ; but that they must be 

 called nitrous salts, has been scarcely called in question, which this experiment 

 and some others contradict. Nitrous salts seem to me not to have any pro- 

 perty of volatile salt : nitre is a salt of so fixed a nature, that it will continue 

 melted in a very strong fire with scarcely any evaporation ; but if you put into it 

 charcoal, or brimstone, or give it an accension, you may obtain a great quan- 

 tity of as fixed a salt as any concrete whatever affords ; so that gold seems not 

 of a more fixed nature. 



Corol. 1. — A standard of volatile salts should be settled ; at present I can 

 think of none better than water. That salt, which in distillation is more fixed 

 than water, ought not to be reckoned among volatile salts : this standard will 

 be justified by good measures, grounded on experience ; for all salts that are 

 truly volatile, are really lighter than water ; that is, in a chemical sense, do with 

 a less degree of fire sublime in our glasses, or come over the helm, than water 

 does. This is justified in the volatile salt of amber, erroneously so called ; for 



• Dr. Slare's views concerning the derivation of the florid colour of arterial blood from the air, 

 and the uses of the atmospheric fluid in respiration, have in part been confirmed by the experi- 

 ments and observations of succeeding physiologists. 



