CIRCULATION OF THE BLOOD. 



28. When blood coagulates, the globules unite themselves to- 

 gether in a mass, and little by little separate from the serum, to 

 form a clot more or less solid. 



[Chemistry teaches us, that in man, 100 parts of blood, contain 

 about 66 parts of water, from 6 to 7 hundredths of albumen, (1), 

 from 14 to 15 nundredths of fihrin, (2), and colouring matter, 

 some thousandths of fatty matters, of several salts, and traces ol 

 the peroxide of iron. Under ordinary circumstances, we cannot 

 discover in the blood, those substances which are found in the 

 different humors, formed at its expense ; but if we arrest the action 

 of those organs that are charged with secreting these humors, we 

 then find in the blood, the matters in question. We must therefore 

 conclude that they always exist in it, but in quantities too small to 

 be appreciated by our methods of analysis; and that the organs just 

 alluded to, do not form them, but separate them from the blood in 

 proportion as they are presented.] 



29. The blood contains all the materials necessary to the re- 

 paration and growth of the organs; consequently, it furnishes to 

 all parts the matter, of which they are in need for their nourish- 

 ment, and also imparts the excitement necessary to the main- 

 tenance of life. 



30. To appreciate fully the importance of the office filled by 

 the blood in the bodies of living animals, it is only necessary to 

 bleed one, and observe the effects of the operation. 



31. When the flow of blood continues for a long time, the 

 animal falls into syncope, (fainting,) and if the bleeding be not 

 arrested, all motion ceases in a few moments ; respiration is 

 stopped, and life is no longer manifest by external sign. If the 

 animal be left in this condition, reality soon takes the place of ap- 

 pearance, and death speedily follows. But if we inject into his 

 veins, blood similar to that which he has lost, we see with astonish- 

 ment this semblance of a corpse return to life ; in proportion as ad- 



(1.) Albumen, is a kind of matter that enters into the composition of most 

 of the organic tissues of animals, and almost by itself constitutes the white 

 of egg's. It can be dissolved in water, but by the action of he.it, it solidifies 

 and becomes insoluble. 



(2.) Fibrin, is the basn of muscular flesh. It can be separated from b'ood 

 by beating it with rods boforo it coagulates; the fibrin adheres to the rods 

 in the form of very elastic whitish filaments. 



28. When blood coagulates what takes place ? 



29. What does the blood contain ? Wiiat other use has the blood besides 

 that of nourishing the organs ? 



30. How can you show the importance of the blood to living animals? 

 .11. How is an animal effected by bleeding ? What is the effect of inject- 



ing blood into the veins of an animal that lias been exhausted by bleeding' 



