CIRCULATING SYSTEM. 34S 
transparent, nearly colourless fluid, surrounding particles 
of a denser substance, and highly coloured. The envelop- 
ing fluid is called Serwm, 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. Apams considered them as ramified, and resembling 
the branches of a tree*. Father D1 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 +. This jointed annular structure 
had been remarked half a century before, by Leruren- 
HOEK, and a figure of the appearance givent. 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 
bleod to be “ as flat. as a guinea.” The dark spot.m the 
middle, which other observers had perceived, he considered 
‘< as a solid particle contained in a fat vesicle, whese 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. 
+ Phil. Trans. vol. lv. p. 255. 
+ Opera Omnia, vol. iii. p. 221. fig. 4. 1, K. 
