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dilation gives to the several particles that constitute 

 the mass of animal fluids. As the velocity of these 

 fluids is increased, the particles of which they consist 

 come oftener into contact, and the oftener the phos- 

 phoreal and aereal meet, the more heat they produce. 

 But to what cause is the colour of the bloodowiug? 

 Borelii took some of the red part, and washing 

 it frequently hi water, found it separable into a vis- 

 cous slippery substance, consisting of colourless fibres 

 which rose and gathered into a scum on the top of 

 the water, arid a deep red powder, which precipitated 

 plentifully to the bottom. Hence it appears that the 

 redness of the blood springs from red tinging par- 

 ticles, as in the case of dying. 



However, this red colour, though generally found 

 in the blood of land. animals, is not absolutely neces- 

 sary, there being some species, whose blood is white 

 or limpid. Nay, Dr. Drake let out of the median 

 vein of 3 man, a pure, white blood, like milk, which 

 when cold, did not separate into two parts, as the 

 red usually does. Nor yet did it yield any skim or 

 cream, neither turn sour as milk uses to do. Dr. Deal 

 gives an instance of the same kind ; and Dr. Lower 

 relates one as strange. A person bled at the nose, 

 till at length the broth he drank flowed out very 

 little altered. 



It is amazing to see, how careful providence has 

 been, to prevent the blood's running into coucre. 

 tions, which might- destroy life, by the very disposi- 

 tions of the vessels it is to run through. These are 

 so contrived, sp as to cause the globules to come 

 together with a brisk collision. The arteries which 

 convey the blood from the heart to the extremities, 

 continually lessen as they recede from their source ; 

 in consequence of which the globules of blood must 

 rush with torce agaii^t one another, as they are driven 

 on impetuously. And the veins which bring it back 

 from the extremities to the heart, enlarging all the 

 if ay as they go on, while the streams of several cou- 

 tinuatiy run into oue ; each of these iugresses causes 



I. K 



