193 



all sorts of flukls. This has two very different mo. 

 tions ; an expansive one, arising from its natural 

 elasticity, by which it gives their fluids an intestine 

 motion, and gradually extends the parts that con- 

 tain them, and a- progressive motion. It does not 

 appear that this is essential to it. Rather it is occa- 

 sioned by the resistance of the solid parts. This, re. 

 straining its expansion, obliges it to take the course 

 that is more free and open, which is through the 

 vessels of plants and animals. 



When this course is stopped, the expansive motion 

 remains and still continues to act, tiil it has so fully 

 overcome the including bodies, as to bring itself to the 

 same degree of expansion with the outward air. But 

 this it cannot do, without destroying the texture 

 and continuity of those solids, which we call corrup- 

 tion. 



The destructive quality of the air is promoted, ei- 

 ther by weakening the tone or cohesion of the in- 

 cluding parts ; as when fruit is bruised, which cor- 

 rupts in that part much sooner than in the others r 

 or by increasing the expansive force of the air, by 

 heat, or some other co-operating circumstance. 



And certainly there is no corruption or putrefac. 

 tion without air. Hence either vegetable or animal 

 bodies buried deep in the earth or. water, remain for 

 ages entire, which when exposed to the air, quickly 

 moulder away, and hence such vegetables as are most 

 apt to putrefy, remain unchanged in vacuo. 



Yet various experiments seem to shew, that air 

 must be impregnated by water, before it can occasion 

 putrefaction, either in animal or vegetable substan- 

 ces. For take a pound of fresh flesh, and keep it 

 in a moderate heat, and it will thoroughly putrify in 

 a few days. But if you first extract the moisture, it will 

 harden like a stone. And it may then be kept for 

 ages, without any putrefaction. Even blood, if you 

 deprive it of its watry part, may be kept for fiftv 

 years* But if you then dissolve it in water, and 

 place it in a gentle warmth ; it will putrefy immediate! v. 



VOL. a. JH: 



