154 THE CIRCULATION 



with mineral salts and water, the latter constituting more than 

 half the bulk. The coloring matter, haemoglobin, has the 

 power of readily absorbing oxygen, wherever that gas is found, 

 and with equal facility parting with it wherever it is needed. 

 Thus it is that the blood in its passage through the lungs 

 absorbs the oxygen from the air, or as much of it as is needed. 

 As the blood circulates throughout the tissues of the body, it 

 supplies them with their needed oxygen. 



9. Besides these corpuscles, 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 millions, and at least five hundred times 

 that number in the whole body. 



10. The white blood corpuscles exist in the blood, in the 

 proportion of about one to three hundred of the red. They 

 are nearly spherical in form, and are about one-half as large 

 again in diameter as the red ones. They consist of a soft, 

 somewhat viscid, finely granular substance, containing one or 

 more ovoid nuclei. They are less yielding and slippery than 

 the red, and adhere more readily to any surface with which 

 they come in contact. If the blood in circulation in the web 

 of the frog's foot be examined, it will be seen that the red 

 globules form the centre of the current, whilst' the white are 

 often seen along the walls of the blood-vessel. They are capa- 

 ble of independent movement, resembling in this the amoeba, 

 already spoken of in the first chapter ; by means of this inde- 

 pendent motion they are enabled to move from place to place, 

 and even pass through the walls of the capillaries into the sur- 

 rounding tissue. Nothing definite is known about their physi- 

 ological functions. That they play an important'part in the 

 economy of the body cannot be doubted as judged from the 

 fact that they are present in such considerable numbers. 

 Some observers claim that they have an important part in the 



9, Si?e, shape, and color of wUite corpuscles ? 10. Proportion of whjte to red corpuscles ? 



