PHYSIOLOGY. 195 



156 of Fahrenheit's thermometer, it concretes into a firm and 

 almost transparent jelly ; and if this be cut into minute pieces, 

 there exudes from it a thin colourless fluid of a saline taste. In 

 proportion as this fluid is more carefully separated, the coagu- 

 lated part becomes more insipid, and in all its properties re- 

 sembles the gluten separated from the crassamentum. From 

 hence, we are ready to conclude, that the serum, as obtained by 

 spontaneous separation, consists of a portion of gluten dissolved 

 in a saline fluid, which we name the SEROSITY. 



CCLIII. From the whole that has been said, from CCXLIV- 

 to CCLII., it appears that there are three distinct portions and 

 kinds of matter in the common mass of blood ; that is, red glo- 

 bules, gluten, and serosity. What other matters may also be 

 there we shall consider afterwards ; but, in the mean time, shall 

 say a little more of each of the parts we have already men- 

 tioned. 



CCLIV. The red globules have been considered as an oily 

 matter, and from thence their distinct and globular appearance 

 has been accounted for ; but there is no direct proof of their 

 oily nature, and their ready union with, and diffusibility in wa- 

 ter renders it very improbable. As being microscopical ob- 

 jects only, they have been represented by different persons very 

 differently. Some have thought them spherical bodies, but di- 

 visible into six parts, each of which, in their separate state, were 

 also spherical ; but other persons have not observed them to be 

 thus divisible. To many observers they have appeared as per- 

 fectly spherical, while others judge them to be oblate spheroids 

 or lenticular. To some they have appeared as annular, and 

 to others as containing a hollow vesicle. All this, with several 

 other circumstances relating to them, very variously represent- 

 ed, show some uncertainty in microscopical observations ; and it 

 leaves me, who am not conversant in such observations, alto- 

 gether uncertain with respect to the precise nature of this part 

 of the blood. The chemical history of it is equally precarious ; 

 and, therefore, what has been hitherto said of the production, 

 and changes happening to these red globules, we choose to leave 

 untouched. We shall afterwards say something with respect to 

 their general use in the animal system ; and now we shall at- 



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