SPECIFIC GRAVITY 25 



SPECIFIC GRAVITY 



Hammerschlag's method is the most simple for obtaining the 

 specific gravity of the blood. A urinometer is partly filled with a 

 mixture of benzene (C 6 H 6 ) and chloroform having a specific gravity 

 of about 1060. With the pipette a drop or two of blood, obtained 

 with the usual precautions, is placed in the fluid. Care must be 

 taken not to expel air with the blood. It is better to have more 

 than one drop present as a drop may stick to the bottom of the 

 vessel. By adding benzene or chloroform the specific gravity of 

 the fluid may be made the same as that of the drops of blood, that 

 is the blood will neither sink nor rise in the fluid. The gravity of 

 the fluid is at once taken in the same manner as for urine. 



TIME OF COAGULATION 



Wright has devised a simple instrument for measuring the time 

 it takes the blood to coagulate. The instrument consists of a 

 reservoir containing a rack holding a thermometer and twelve 

 calibrated glass tubes. The tubes are placed in the reservoir, 

 which contains water at a desired temperature (18.5 or 37° C) and 

 allowed to remain until they become of the same temperature. 

 Then they are dried, five cc. of blood drawn into each, and re- 

 placed in the reservoir. At varying intervals the tubes are ex- 

 amined by attempting to blow out the blood. When the blood 

 cannot be expelled, coagulation may be considered as complete. 



There are several other methods of obtaining the time of co- 

 agulation. In Hinman and Sladen's modification of Milian's 

 method glass slides are used. Any glass surface will do. The 

 puncture is made in the usual manner. The first drop is wiped 

 off and time counted from the appearance of the second drop. The 

 under surface of a slide is touched lightly to the drop of blood in 

 two or three places. Coagulation is considered complete when 

 tilting the slide produces no change in the slope of the drop of 

 blood. The drops at different examinations should be of about 

 the same size, 3, 4, 5 or 6 mm. in diameter. Coagulation takes a 

 longer time with larger drops, longer with 6 mm. than with 3 mm. 

 drops. 



Bogg's modification of the Brodie-Russell method is a slide 



