264 THE INCOME OF ENERGY 



II BLOOD 



SPECIFIC GRAVITY 



Drawing the Blood. Wash the lobe of the ear 

 with a bit of absorbent cotton dipped in clean 

 water. 1 Eub the lobe dry with another piece 

 of cotton. Pass a three-sided surgical needle 

 through a Bunsen flame. (Do not heat the 

 needle red or the temper will be drawn and the 

 sharpness lost.) Stretch the skin of the lobe 

 between the fingers of the left hand. Make a 

 quick puncture one -eighth inch deep in the edge 

 of the lobe. Press gently to start the flow. The 

 blood must now flow freely. On no account use 

 blood squeezed out. 



Determination of Specific Gravity. 2 Fill a 

 small beaker half full of a mixture of benzol and 

 chloroform of a specific gravity of about 1059. 

 Let a drop of the blood fall into this mixture. 

 The drop will remain spherical, for blood does 

 not mix with benzol and chloroform. If the 

 drop sinks, add chloroform drop by drop, mean- 

 while stirring the mixture with a glass rod, until 



1 Subjects who are " bleeders" are not to be used for this 

 observation. 



2 ROY: Journal of Physiology, 1884, v, p. ix. HAM- 

 MERSCHLAG, A. : Wiener klinische Wochenschrift, 1890, iii, 

 p. 1018. 



