THE RED BLOOD CORPUSCLES 185 



the isolation of these crystals, are those described by Hoppe-Seyler 

 as well as by Reichert and Brown. ^ 



The crystals so obtained are red in color and transparent. Although their size 

 is generally microscopic, they may attain a length of 2 to 3 mm. They appear 

 as prisms, platelets, tetrahedra and needles of the rhombic system. From the 

 blood of squirrels six-sided plates of the hexagonal system are usually obtained; 

 moreover, it is possible to change these into rhombic prisms and tetrahedra by the 

 process of recrystallization. They may be heated to 110-115° C. without decom- 

 position, but when subjected to a temperature of about 160° C, a reduction results, 

 the ash yielded during this process being composed largely of oxid of iron. They 

 are soluble, but not in an equal measure, because those most difficult to produce 

 are most readily dissolved. Very dilute solutions of the carbonates of alkalies a e 

 the most efficient solvents. Hemoglobin is not easily dialy zed. It does not diffuse 

 through parchment membranes and shows a behavior similar to that of colloidal 

 bodies. 



Reduced hemoglobin is more soluble than oxyhemoglobin. Its crystals are 

 not easily obtained. They are isomorphous to the corresponding crystals of 

 oxyhemoglobin and are darker in color and pleochromatic. 



The hemoglobin content of the blood amounts to about 14 per cent, in man and 

 to 13 per cent, in woman. Thus, an individual weighing 70 kilos, contains about 

 2684 grams of blood and about 491 grams of hemoglobin. This amount is dis- 

 tributed among 25,000,000,000,000 red corpuscles which present a total surface of 

 about 3200 square meters. Moreover, as these bodies are usually well scattered 

 and traverse the capillaries almost "in single file,'' practically all of the hemo- 

 globin is made available for respiratory purposes. It is also of interest to note 

 that blood absorbs a much greater quantity of oxygen than water. Thus, while 

 100 c.c. of the latter take up only 0.7 c.c, 100 c.c. of human blood assimilate 

 18.5 c.c. of this gas. The amount of hemoglobin present in the blood of the fetus 

 or infants, is much greater than that found in the blood of adults. 



Properties of the Compounds of Hemoglobin with Oxygen. — The 



function of hemoglobin, to distribute the oxygen to the different tissues 

 of the body, depends upon its ability to unite with perfectly definite 

 amounts of this gas. This union takes place in the lungs, where this 

 substance is exposed to the full pressure of the oxygen of the atmos- 

 pheric air. Having absorbed its quota of the gas, it is moved onward 

 to the distant tissues. Here the oxygen is required for purposes of oxi- 

 dation, and hence, inasmuch as it is present in smaller amounts in the 

 cells than in the blood, it must be held under a greater partial pressure 

 in the blood-vessel than in the tissue. As a direct result of this differ- 

 ence in its partial pressure, it separates from the hemoglobin and enters 

 the cells. The oxyhemoglobin is thus converted into its deoxidized 

 or reduced variety. This property of the hemoglobin to assimilate 

 and to release a part of its oxygen, forms the basis of the respiratory 

 activity of the blood. 



The compound of hemoglobin and oxygen, known as oxyhemoglobin, can also 

 be formed and destroyed outside of the body. Thus, if arterial blood is exposed to 

 a vacuum, it f rothes and its color changes to bluish red in accordance with the 

 amount of oxygen withdrawn from it. Quite similarly, if venous blood is shaken 



^ The characteristics of the crystals of hemoglobin from different animals are 

 described by Reichert and Brown, in: The Crystallography of Hemoglobins, 

 Carnegie Inst, of Washington, No. 116, 1909. 



