228 RED PARTICLES 



times have viewed them through a microscope, and have con- 

 cluded them spherical, if they be really flat. But however that 

 may have happened, it is a fact that they are as flat in the body 

 as out of it. Of this I am convinced, by having repeatedly 

 observed them, whilst circulating in the small vessels, between 

 the toes of a frog, both in the solar microscope and the more 

 simple one above mentioned. I have seen them with their 

 sides parallel, like a number of coins laid one against 

 another (cix). 



I have likewise, in that animal where they are elliptical, seen 

 them move with one end foremost, and sometimes with an edge 

 turned towards the eye. I have moreover seen them, when 

 entering a small vessel, strike upon the angle between it and 

 the larger trunk, and turn over with the same variety of phases 

 that they have when turning over upon a piece of glass. 



Upon this occasion I may remark that it has been said by 

 some microscopical observers, that in passing through very 

 small vessels they seem to alter their shape, and to be 

 lengthened. 



This conclusion I suspect has taken its rise from the observer 

 having seen them with their edge turned towards his eye, in 

 which case they would appear long and small, as if lengthened 

 by compression, especially to one who sets out with the notion 

 of their being globular. I have seen them, in blood-vessels 

 which would admit only single vesicles, move with difficulty, as 

 if straitened for room, but never saw them altered in their 

 shape by the action of the vessels (ex) . 



(cix.) When the blood of a mammal is drawn, most of the corpuscles 

 soon run together so as to resemble a roll of coins ; only a few of the cor- 

 puscles are irregularly connected like a shapeless heap of money. It is 

 in this latter way that the oval corpuscles of the lower vertebrata and of 

 the camelidee connect themselves together, and not with the curious regu- 

 larity of the columns of the circular corpuscles of mammalia, mentioned 

 in Note c. Hewson appears to be describing the human blood-corpuscles 

 laid one against another like coins, because he is arguing for the flatness 

 of these corpuscles, which, as he previously states (p. 214), had been 

 long before known of the larger corpuscles of fishes and amphibia. 



(ex.) The older observers, as Leeuwenhoek, a William Cowper, b and 

 Senac, c were certainly right in describing the corpuscles as pliant or 



a Phil. Trans. 1675, x, 380. c Traite du Coeur, ed. 1749, t. ii, pp. 81, 



b Phil. Trans. 1702, xxiii, 1184. 657 ; and 2d ed. t. ii, p. 277. 



