20 PHYSIOLOGY FOR NURSES 



certain substances which resemble ferments in their ac- 

 tion. Among the latter may be mentioned protlirom- 

 bin, which, as we shall see, is active, in causing blood- 

 clotting or coagulation. 



Of the formed elements of the blood, the red corpus- 

 cles or erythrocytes are the most numerous. There are 

 about five million of these to the cubic millimeter of the 

 blood of a healthy man ; women are supposed to have 

 about five hundred thousand less. They contain a sub- 

 stance known as hemoglobin, which, by virtue of its 

 iron content, is capable of forming unions with gases, 

 especially with oxygen, and to a less extent with car- 

 bon dioxide. These unions, as we shall find, are essen- 



Small Large Polymorphic Polynuclear. Eosinophile. 



mononudear. monomiclear. 



Fig. 2. White blood-corpuscles from man. (Hill's Histology.) 



tial for the processes of respiration. The number of 

 these corpuscles is reduced under certain pathologic 

 condition, as in the various anemias; and may be in- 

 creased when there is a great loss of fluid from the body, 

 as in cholera or where there is a diminution in the 

 amount of oxygen in the surrounding air, as in ascents 

 to great heights. 



The white cells serve an entirely different function in 

 the body. There are from five to ten thousand to the 

 cubic millimeter of blood on the average, but this num- 

 ber is subject to wide variations under altered condi- 

 tions. The white cells are of assistance in the digestion 

 of protein and in the transportation of fat in the blood, 



