THE CIRCULATION 



59 



liquid itself is seen to be almost as clear as water. This 

 liquid is called the plasma. Floating in it are millions of 

 biconcave disks contain- 

 ing a pigment (hemo- 

 globin) which gives the 

 red color to the blood. 

 The disks are called red 

 corpuscles (Fig. 60). A 

 few irregularly shaped 

 bodies, nucleated and 

 almost transparent, and 

 called white corpuscles, 

 are also found in the 

 blood. The red corpus- 

 cles go only where the 

 plasma carries them 

 (Exps. 3, 4). The white 

 corpuscles sometimes leave the blood vessels entirely. 

 At times one may be seen shaped like a 

 dumb-bell, half of it through the wall of 

 the blood vessel and half still in the 

 blood vessel. After the corpuscle is 

 out, no hole can be found to account 

 for its mysterious passage. The white 

 corpuscles consist of protoplasm. The 

 red corpuscles contain no protoplasm. 

 Hence the latter arc not really alive. 



The Use of Each Part of the Blood.— 

 The plasma keeps the blood in a liquid 

 state, so that it may flow readily ; the 

 plasma also transports the food that has 

 been eaten and digested, and carries carbon dioxid to the 

 lungs and other waste material to the kidneys. The red 



Fig. 6o. — Human Blood Cells (magni- 

 fied 40,000 areas), showing many red cells 

 and a single white blood cell on left, larger 

 than red cells. (Peabody.) 



Fig. 61. — Side and 

 Front Views of 

 Frog's and Man's 

 Red Corpuscles, 

 drawn to same 

 scale. Compare 

 outline, concavity, 

 diameters. 



