LABORATORY MANUAL OF PHYSIOLOGY. 



The necessary apparatus consists of a urinometer jar, urino- 

 meter, a pipette of small calibre, glass rod, fine steel pens, bottle of 

 chloroform, benzol, and a mixture of the two. The mixture 

 should be approximately that of the estimated specific gravity of 

 the blood to be tested. 



A drop of blood is sucked up into the pipette. This is gently 

 blown out below the surface of the mixture, care being taken to 

 leave some blood in the pipette. It is well to have several drops in 

 the mixture. If the specific gravity of the blood and that of the mixt- 

 ure is the same, the drop will float indifferently wherever placed. 

 If the specific gravity of the mixture is greater than that of the blood 

 dropj the latter will rise. If the mixture is lighter than the drop, 

 the latter will sink. The density of the mixture may be increased 

 by adding chloroform and decreased by adding benzol. The 

 mixing of the two fluids is accomplished by careful stirring with a 

 glass rod. When the density of the blood and that of the con- 

 taining mixture is the same the specific gravity is taken by means 

 of the urinometer. 



The same chloroform-benzol mixture may be used repeatedly, 

 if filtered after each test. Scrupulous cleanliness must be observed. 

 Otherwise, particles of dust might adhere to the blood drop and 

 thus cause an error. Care should also be taken to avoid the ad- 

 mixture of air with the drop of blood. The reading should, like- 

 wise, be taken as soon as possible, to avoid error through vapor- 

 ization and through changes in the blood drop. If the hydrometer 

 jar is not perfectly clean, the globule of blood is liable to adhere to 

 the sides. 



The advantages of this method of haemoglobin determination are 

 obvious. There is no delicate color comparison to be made. If 

 proper precautions are taken, the experimental error is very small 

 as compared with the color methods. The apparatus is simple and 

 inexpensive and the technique is not difficult. 



Estimate the haemoglobin of a fellow-student by the several 

 methods given above and compare results. 



[72] 



