OF THE BLOOD. 221 



particles are spread out on a glass, they run in clusters, and 

 stick to each, other, and then they appear confused (c). 



When one of these particles is attentively examined, while 

 separate from the rest, it appears, as it lies on its flat side, to 

 have a dark spot (ci) in the middle, and round that dark spot 

 it is more transparent. This dark spot was believed to be a 

 perforation, or the particle was supposed to be a hollow ring, 

 by the ingenious Father de la Torre. But I find from a great 

 number of experiments, that the dark spot is a solid particle 

 contained in a flat vesicle, whose middle only it fills, and whose 

 edges are hollow, and either empty or filled with a subtile fluid. 

 This will be evident to every one who will carefully make the 

 following experiments. 



EXPERIMENT II. 



Take a drop of the blood of an animal that has large particles, 

 as a frog, a fish, or what is still better, of a toad ; put this blood 

 on a thin piece of glass, as used in the former experiment, and 

 add to it some water, first one drop, then a second, and a third, 



(c.) Further on, a Hewson says he has seen them laid one against 

 another like a number of coins ; and the way in which the corpuscles 

 of mammalia run together by their broad surfaces, forming piles like 

 rolls of money, has become well known since the clear description of 

 the fact by Dr. Hodgkin and Mr. Lister. b The earliest representation 

 which I have seen of these rolls of the corpuscles is that by Delia Torre, c 

 three years after the publication of llewson's observations. Mr. Wharton 

 Jones d has figured the rolls ; and I have depicted 6 parts of them on a 

 larger scale, from the blood of man and of the horse. These rolls fur- 

 ther coalesce into clumps in bufly human blood, and still more remark- 

 ably in the naturally buify blood of the horse : see Note xxni. The 

 aggregation commences as soon as the blood is drawn, goes on after two 

 or three minutes at a greatly accelerated rate, and subsequently some of 

 the corpuscles separate again from the piles. Dr. Davy f has particularly 

 described the viscid quality of the corpuscles as distinct from that by 

 which they form into columns ; they stick together at their rims, so 

 that the corpuscles, when separating from each other, become elongated 

 almost into a fibre, and recover their circular form when completely 

 detached. I have frequently observed these appearances in corpuscles 

 which have been kept a day or two in the serum. 



(ci.) See Note xcvi, p. 216. 



a See Note cix, p. 228. * Edin. Med. and Surg. Journ. Ix, 311. 



b Phil. Magazine, 1827, vol. ii, p. 135. e Lond. and Edin. Phil. Mag., Aug. and 

 1 Xuove Osservazione Microscopiche, Sept. 1842, pp. 109, 170. 



tab. xiv, fig. 4, 4to, Napoli, 1776. f Trans. Royal Soc. Edin., xvi, 54-5. 



