THE CIRCULATION 



153 



a pearl button that has not been perforated. In freshly-drawn 

 blood they show a disposition to arrange themselves in little 

 rolls like coins (Fig. 33). 



6. The size and shape of blood (red) corpuscles, vary in dif- 

 ferent animals. In man they are circular and flat, with a central 

 depression on both sides, also in all warm-blooded quadrupeds, 

 except the camel and lama, where they are oval. In birds, 

 reptiles, and fish, they are oval, but with 



raised centre or nucleus. .This variation is (& *" 



often of vital importance in murder trials, ^ 



where blood-stained weapons or clothing are 

 used as evidence. A microscopical examina- 

 tion shows us the corpuscles, and we deter- 

 mine from their shape, whether it was caused 

 by blood from a warm-blooded quadruped, 

 from a camel, or from a fowl or fish. But 

 we cannot affirm that the stain was made by 

 human blood, and not by that of the dog, ox, 

 or sheep, because in all of these the corpuscles 

 are shaped alike, and the size varies but little. 



7. The character of the blood of dead, ex- 

 tinct, and even fossil animals, such as the corpuscles o'f a 'frog, c', 

 mastodon, has been ascertained by obtaining T ^e file sm^n ones at 

 and examining traces of it which had been the upper part of the 

 shut up, perhaps for ages, in the circulatory ^7^^"! m^n"- 

 canals of bone. A means of detecting blood fled four hundred times. 

 in minute quantities is found in the spectroscope, the same 

 instrument by which the constitution of the heavenly bodies 

 has been studied. If a solution containing not more than one 

 one-thousandth part of a grain of the coloring matter of the 

 corpuscle be examined, this instrument will detect it. 



8. The red corpuscles are of a soft and jelly-like consistency, 

 without any distinctive cell membrane enclosing them. Some 

 observers have claimed that this latter does exist, but it can- 

 not be demonstrated. They are composed of an albuminous 

 substance and a coloring matter, called haemoglobin, together 



Fie. 84. a, Oval 

 Corpuscles of a fowl. 6, 



6. Size and shape of the red corpuscles ? 7. How may blood in minute quantities be 

 ietectd 1 8. Describe the structure and constitution of the red corpuscles. 



