110 NUTRITIONAL PHYSIOLOGY 



abound in the enlarged extremities of the long bones. 

 Here there is always going on a progressive change in the 

 composition of the cells, in course of which hemoglobin 

 replaces most of their original substance. The cell nuclei 

 are eventually lost and the newly formed corpuscles de- 

 tach themselves and drift away in the blood-stream. Their 

 hollow centers strongly suggest the deficiency due to the 

 loss of the nuclei. It is an interesting fact that when re- 

 covery is taking place after hemorrhage, red corpuscles 

 containing nuclei are often to be found in samples of the 

 blood. This makes it seem as though in meeting the emer- 

 gency corpuscles in an incomplete stage of their devel- 

 opment had been pressed into service. 



The first glance at a specimen of blood under the micro- 

 scope leaves the impression that the corpuscles are all of one 

 unvarying type. Closer observation shows here and there 

 among the host of colored elements bodies of another or- 

 der, the white or colorless corpuscles. There is but one of 

 these to 500 or 1000 red. The white corpuscles are not 

 flattened, but more nearly spheric. They are, however, 

 of no fixed form, and many of them have the property of 

 ameboid movement. This is good evidence that they are 

 to be considered living, and it can be shown further that 

 they have nuclei and conform to our conception of com- 

 plete cells. Much that is of interest is known of them, and 

 the relation which they bear to the checking of bacterial 

 infection is of the utmost importance. We shall not enter 

 upon a discussion of this fascinating subject. 



The Plasma. Aside from the transportation of oxygen, 

 all the chief functions of the blood could apparently be 

 fulfilled by the plasma. The standard foods of the tissues 

 are here. So also in much smaller amounts are the non- 

 gaseous wastes. Carbon dioxid, the most abundant of all 

 waste-products, is carried jointly by the plasma and the 

 corpuscles. It is evident that we must expect a solution 

 meeting such manifold requirements to be of a highly 

 complex nature. This is eminently the case. 



More than nine-tenths of the plasma is water. The 



