222 



HITCHCOCK'S ANATOMY 



in health, as the red corpuscles. But in certain diseases, and 

 especially if there be a wound in any part of the body to be 

 healed, the white corpuscles are developed at a great rate, 

 although their abundance ceases when the system is restored 

 to a sound state again. Their average diameter is nearly 

 3 oVoth of an inch, and they appear to be nucleated cells. The 

 proportion of the white to the red corpuscles in health is nearly 

 as 1 to 346. The whole amount of blood corpuscles has been 

 estimated as high as 65,570,000,000,000. 



384. Effect of an Alternate Exposure to Oxygen and 

 Carbonic Acid , — If the red corpuscles are alternately exposed 

 to oxygen and carbonic acid they lose their circular form, 

 and become corrugated or star-shaped, and finally are destroyed ; 

 and it is calculated that millions of these corpuscles are de- 

 stroyed at each pulsation of the heart. 



FUNCTIONS OF THE CIRCULATORY SYSTEM. 



385. The Main Use of the Blood-Vessels — The large 

 Angle made by the Arterial Branches near the Heart. — 

 The first and most obvious use of the blood-vessels is to allow 

 a free and rapid passage of this fluid to every part of the 

 body. This is evident from the smooth lining of all the ar- 

 teries and veins, and from the fact that, with the exception of 

 the large arteries near the heart, the vessels branch off at a 

 small angle from each other, which arrangement offers the 

 least possible obstruction to the passage of the blood. In the 

 organs near the heart, as the head and lungs, the blood would 

 readily pass by smaller vessels and by less force of the heart 

 in sufficient quantity. But in that case the parts of the body 

 quite distant' from the center of circulation of the blood would 



When are the white ones the most abundant? State the approximate number of bloo^ 

 corpuscles in one individual. 3S4. What effect has an alternate exposure of oxygen and 

 carbonic acid upon these ? How many are possibly destroyed at each pulsation of tho 

 heart ? 385. Give the use of the arteries and veins. 



