VIR*M.M.ATIN<; SYSTKM. 341 



transparent, nearly colourless fluid, surrounding particles 

 of a denser substance, and highly coloured. The envelop- 

 ing fluid is called Serum, and the bodies which are sus- 

 pended in it the Particles, or Globules of the blood. 



A great difference of opinion has prevailed among natu- 

 ralists, with regard to the form and structure of the coloured 

 particles of the blood. Although making use of the same 

 kind of instrument, and professing to abide by the evidence 

 of the senses, their statements exhibit very remarkable diffe- 

 rences. ADAMS considered them as ramified, and resembling 

 the branches of a tree *. Father Di TORRE, with a spheri- 

 cal lens, which magnified 512 diameters, regarded them as 

 oblate spheroids, much compressed, with the middle part 

 much darker than the margin. With a magnifying power 

 of 1280 diameters, he considered them as perforated in the 

 centre, and the surrounding ring as composed of joints from 

 two to seven in number -f. This jointed annular structure 

 had been remarked half a century before, by LEEUEN- 

 HOEK, and a figure of the appearance given J. HEWSON, 

 who appears to have conducted his observations with cau- 

 tion, and used lenses which magnified the diameter of ob- 

 jects from 184 to 1280 times, considered the particles of 

 blood to be " as flat as a guinea." The dark spot in the 

 middle, which other observers had perceived, he considered 

 " as a solid particle contained in a flat vesicle, whose mid- 



" Human blood is so far from shewing any Red Globules swimming 

 in Serum, that immediately after its Emission, it appears to be a Body of 

 infinite Branches, running in no certain order, variously coloured : where it 

 lies thickest on the glass, it's of a Red, where thin, inclining to Yellow.; but 

 the whole so blended, as to represent, very near, the top of a Yew-tree in a 

 very fine landskip, having its supposed Branches of a Red and Yellow con- 

 fusedly intermixt." Phil. Trans, vol. xxvii. p. 26. 



f Phil. Trans, vol. lv. p. 255. 



Opera Omnia, vol. iii. p. 221. fig- 4-. I, K. 



