VENOUS AND ARTERIAL BLOOD. 33 



37. Consequently, there is a very great difference between the 

 blood going to the organs, and that which has already passed 

 through them, and which has contributed to their, nourishment. 



38. To the first is given the name of untr.at 6.000, and to the 

 second, the name of venous blood. 



39. Arterial blood is of a vermilion red ; it coagulates very 

 easily and contains a large proportion of globules ; and finally, it 

 is essentially necessary to the maintenance of life. 



40. Venous blood is of a blackish red color; it is. less coagula- 

 ble and less rich than the arterial blood, but what distinguishes it 

 above every other quality, is, that after having passed through 

 them, it is no longer capable of exciting the vital movement in the 

 organs. 



41. Notwithstanding, the blood thus vitiated does notecase 

 to be useful, because it easily regains its vivifying qualities. 



42. By action of the air, the venous blood is changed into arte- 

 rial blood ; it regains its vermilion color, and becomes again fit 

 for the maintenance of life. 



43. It is this transformation of venous blood into arterial blood, 

 which constitutes the phenomenon of respiration. 



LESSON III. 



Functions of Nutrition Circulation of the. Blood- the Heart 

 Arteries Veins Motion of the blood in the bodies of the 

 Mam mi force Mechanism of the circulation Phenomenon oj 

 the pulse Venous absorption Secretion. 



CIRCULATION OF THE BLOOD. 



1 . The blood does not remain at rest in the body ; it is con- 

 stantly passing through the organs which it nourishes, and re- 

 turning to the respiratory apparatus to come in contact with the 

 air, to be again distributed to the organs. 



37. Is the blood when it con es from an organ in the same condi'ion aa 

 when it entered >. 



38 What is the blood ca led that goes to the organs ? What is it called 

 when it ln left the orgnns 1 



3!'. \V hat art- the properties of artcrnl b'ood? 



40. What ore t e properti s of the ven us blood? What is the essential 

 quality that distinguishes venous from arterial i.lood/ 



41. Why does blood thus vitiated cease to be useful ? 



42. Tiow is venous blood changed into artetial? 



43. What does this transformation of venous into arterial blood constitute 1 

 1. Is the blood at rest in the body? 



3* 



