42 



ELEMENTS OF HIFi'OLOGY. 



lets — the termination of the veins that carry the blood back 

 to the heart. 



Figure 29 shows, highly magnified, a healthy, living mem- 

 brane of a frog. The broad band, aa, on the left of the cut, is 

 a veinlet; c is a capillary. The lighter^colored disks in the ves- 

 sels and in „ 

 the con- 

 necting tis- 

 sues are 

 white cor- 

 puscles; the 

 darker ones 

 are red cor- 

 puscles. 



Ordinari- 

 ly, the red 

 corpuscles 

 float in the 

 center o f 

 the current, 



while the white ones, due to a certain volition of their own, 

 float along near the walls of the capillaries. The nutrition, re- 

 ceived into the blood from the digestive apparatus, as will be 

 shown later on, replaces worn-out tissues. The oxygen of the 

 red corpuscles is consumed in maintaining the heat of the 

 body, and the blood flows on, taking with it the dead cells of 

 worn-out tissues, the red corpuscles, largely deprived of their 

 oxygen, and the white corpuscles, with their burden of absorbed 

 germs, through the veins in a steady stream to the heart. From 

 there it is pumped into the lungs, blue in color and exhausted of 

 vitality, to be vitalized with oxygen and relieved of its waste 

 matter. From the lungs it goes back to the heart again, purified 

 and enriched, to repeat its function. As the result of repeated 



Figure 29. 



-Highly Magnified Living Membrane 

 of a Frog, Non-inflamed. 



