1 86 MICROMETRY AND BLOOD PREPARATIONS 



In Biirker's test you mix a drop of blood and a drop of distilled water on a slide 

 and with a capillary tube sealed off at the end stir the mixture every half minute. 

 So soon as fibrin threads appear you have coagulation. 



SPECIFIC GRAVITY or THE BLOOD. 



Hammerschlag has a method for the determination of the Hb. 

 percentage based upon the specific gravity of the blood. 



In this method a mixture of benzol and chloroform is made of a specific gravity 

 of about 1050. A medium size drop of blood is then taken up with a pipette and 

 dropped into the mixture. If it sinks add more chloroform from a dropping bottle, 

 if it tends to rise, more benzol. The mixture in which the drop of blood tends to 

 remain stationary, near the top of the mixed benzol and chloroform, has the same 

 specific gravity as that of the blood. This is determined by an accurately graduated 

 hydrometer. The normal average specific gravity for men is 1059, for women 1056. 

 A table, giving the Hb. percentage corresponding to the specific gravity accom- 

 panies the outfit. 



To determine the necessity for intravenous infusion in cholera Rogers has re- 

 cently recommended the employment of small bottles containing aqueous solution 

 of glycerine with specific gravities varying from 1048 to 1070, increasing the specific 

 gravity in each successive bottle by 2. 



An accurate urinometer will suffice to determine the specific gravity. Drops 

 of blood from the cholera patient are deposited at the center of the surface of the 

 fluid in the bottles from a capillary pipette. If the specific gravity of the blood is 

 1062 at least a liter of saline or sodium bicarbonate solution is needed. If 1066 at 

 least two liters. Formerly he estimated the indications by blood pressure con- 

 sidering a pressure of 80 in Europeans 01 of 70 in natives as indicating intravenous 

 injections. 



OCCULT BLOOD. 



When the presence of blood cannot be recognized by macroscopical 

 or microscopical methods (occult blood) we must resort to spectro- 

 scopic or chemical tests. It is in connection with blood in the faeces 

 that these tests for occult blood are chiefly called for. Before making 

 such tests on faeces it is advisable to have the patient on a meat-free 

 and green-vegetable-free diet for two or three days. It is chiefly in 

 carcinoma or ulcerations of the gastro-intestinal tract that such exami- 

 nations of the faeces are required. 



Haemin Crystal Test (Teichman). Prepare a solution of o.i gram each of KI, 

 KBr, and KCL in 100 c.c. of acetic acid. This is a stable solution. Mix some of 

 the material with a few drops of the solution on a slide, apply a cover-glass and 

 warm the material until bubbles begin to appear (gentle steaming), then examine 

 for dark-brown crystals. 



