104 THE CIRCULATION. 



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-thousandth part 

 of a grain of the coloring matter of the corpuscle, be ex- 

 amined, this instrument will detect it. 



8. The corpuscles, just described, are known as the red 

 blood corpuscles. Besides these, and floating along in the 

 same plasma, are the white corpuscles. These are fewer 

 in number, but larger and globular in form. They are 

 colorless, and their motion is less rapid than that of the 

 other variety. The total number of both varieties of these 

 little bodies in the blood is enormous. It is calculated that 

 in a cubic inch of that fluid there are eighty-three mil- 

 lions, and at least five hundred times that number in ^he 

 whole body. 



9. Coagulation. The blood, in its natural condit n 

 in the body, remains perfectly fluid; but^ within a fe r 

 minutes after its removal from its proper vessels, whether 

 by accident or design, a change takes place. It begins to 

 coagulate, or assume a semi-solid consistence. If allowed 

 to stand, after several hours it separates into two distinct 

 parts, one of them being a dark red jelly, the coagulum, 

 or clot, which is heavy and sinks: and the other, a clear, 

 straw-colored liquid, called serum, which covers the clot. 

 This change is dependent upon the presence in the blood 

 of fibrin, which possesses the property of solidifying under 

 certain circumstances; one of these circumstances being 

 when the blood is separated from living tissues. The color 

 of the clot is due to the entanglement of the corpuscles 

 with the fibrin. 



10. In this law of the coagulation of the blood is our 

 safeguard against death by haemorrhage, or against undue 

 loss of blood. If coagulation were impossible, the slight- 



8. White corpuscles ? Total number of corpuscles in the body ? 



9. The blood in its natural condition in the body ? Describe the process by 

 which the coagulation of blood takes place ? 



1 0. If coagulation were impossible ? How is it in fact ? 



