GENERAL PROPERTIES: THE CORPUSCLES. 391 



each corpuscle becomes exposed more or less completely to the action 

 of the air, and the utilization of the entire quantity of hemoglobin 

 must be nearly perfect. It may be worth while to call attention to 

 the fact that the biconcave form of the red corpuscle increases 

 the superficies of the corpuscle and tends to make the surface 

 exposure of the hemoglobin more complete. Instruments known 

 as hemometers or hemoglobinometers have been devised for clinical 

 use in determining the amount of hemoglobin in the blood of 

 patients. A number of different forms of this instrument are in 

 use. In all of them, however, the determination is made with a 

 drop or two of blood, such as can be obtained without difficulty 

 by pricking the skin. The amount of hemoglobin in the withdrawn 

 blood is determined usually by a colorimetric method, that is, its 

 color, which is due to the hemoglobin, is compared with a series of 

 standard solutions containing known amounts of hemoglobin, or 

 with a wedge of colored glass whose color value in terms of hemo- 

 globin has been determined beforehand. For details of the structure 

 of the several instruments employed and the precautions to be 

 observed in their use reference must be made to the laboratory 

 guides.* 



Compounds with Oxygen and other Gases. Hemoglobin has 

 the property of uniting with oxygen gas in certain definite propor- 

 tions, forming a true chemical compound. This compound is known 

 as oxyhemoglobin] it is formed whenever blood or hemoglobin 

 solutions are exposed to air or otherwise brought into contact with 

 oxygen. Each molecule of hemoglobin is supposed to combine with 

 one molecule of oxygen. According to a determination by Hiifner,t 

 the capacity of the Hb of ox's blood is 1.34 c.c. O to each gram of 

 Hb. Oxy hemoglobin is not a very firm compound. If placed in 

 an atmosphere containing no oxygen, it is dissociated, giving off 

 free oxygen and leaving behind hemoglobin, or, as it is often called 

 by way of distinction, "reduced hemoglobin" This power of com- 

 bining with oxygen to form a loose chemical compound, which in turn 

 can be dissociated easily when the oxygen pressure is lowered, makes 

 possible the function of hemoglobin in the blood as the carrier of 

 of oxygen from the lungs to the tissues. The details of this process 

 are described in the section on Respiration. Hemoglobin forms 

 with carbon monoxid gas (CO) a compound, similar to oxyhemo- 

 globin, which is known as carbon monoxid hemoglobin. In this 

 compound also the union takes place in the proportion of one 

 molecule of hemoglobin to one molecule of the gas. The compound 

 formed differs, however, from oxyhemoglobin in being much more 

 stable, and it is for this reason that the breathing of carbon monoxid 



*See Simon, " A Manual of Clinical Diagnosis." Philadelphia, 1904. 

 t "Archiv f. Physiologic," 1894, p. 130. 



