16 WONDERS OF ORGANIC LIFE. 



have gradually subsided during the progress 

 of coagulation. When examined under a mi- 

 croscope of great power, this mass is found to 

 be composed of extremely minute corpuscles, 

 varying in size in different animals. These 

 corpuscles are in the form of flattened discs, 

 circular, oval, or elliptical, and surrounded by 

 a most delicate envelope. According to Mr. 

 Lister and Dr. Hodgkin, these red particles are 

 solid flattened bodies, without any envelope. 

 In the lower vertebrate animals, however, there 

 is a distinct and permanent capsule surrounding 

 a nucleus. In the human subject these blood- 

 discs are circular, flattened, and rather concave 

 on each side, with a rounded margin. Wollaston 

 estimates them at the five-thousandth part of an 

 inch in diameter ; others, however, give dif- 

 ferent estimates of their admeasurement, and 

 among them Hodgkin and Lister, who set down 

 the size as three thousand. It would appear, 

 however, that some variableness as to size in 

 the blood-discs of the same clot is observable ; 

 hence, perhaps, arises the discordance in ques- 

 tion. Within the last few years Mr. Gulliver 

 has devoted great attention to this subject ; * 

 and it appears, from this gentleman's observa- 

 tions, that in the mammalia generally the blood- 

 discs are circular, but in some oval. In birds, 

 reptiles, and fishes, their figure is either oval 



* "We refer to the Med. Chir. Trans., vol. xxiii. Dublin 

 Med. Press, Nov. 27, 1839. Annals of Nat. Hist., Dec. 1830. 

 Lond. and Edin. Phil. Mag., 1839. Appendix to Gerber's 

 Anatomy. The Proceeds. Zool. Soc. Lond. 1840 to 1846, etc. 



