W. W. Palmer 121 
Method. 
Blood is obtained in the usual manner by pricking the finger 
or lobe of the ear. A 1 per cent solution of blood is made by 
drawing 0.05 cc. into a special pipette and transferring into 5 cc. 
of 0.4 per cent ammonia solution—accurately measured with a 
calibrated pipette or burette into a 12 x 120 mm. test-tube. 
The blood pipette is rinsed out by drawing into it two or three 
times the ammonia solution. Ordinary illuminating gas is bubbled 
rapidjy through the ammonia blood solution for 30 seconds, after 
which, it is compared in a Duboscq colorimeter with a standard 
carbon monoxide hemoglobin solution set at 10. The average 
of at least four readings is taken. The calculation is simple, 
an 100 = per cent hemoglobin. 
Manner of Obtaining Blood.—With sufficient care the usual 
clinical method for obtaining small amounts of blood by pricking 
the ear or finger is satisfactory. A free flow is essential. Any 
undue manipulation or squeezing of the part should be avoided 
because an error of 5 or 10 per cent may be introduced by diluting 
the blood with tissue juice. Where there is marked anemia re- 
quiring larger amounts of blood than 0.05 cc., or where there is 
difficulty in obtaining blood from the ear or finger, venous punc- 
ture should be used, coagulation being prevented with oxalate or 
citrate salts. It is often practical and convenient to combine 
the determinations of hemoglobin with other blood analyses, 
where venous puncture is required. If blood has been drawn by 
venous puncture care must be taken that the corpuscles and 
serum are well mixed before filling the pipette. The blood should 
never be shaken violently before measuring, because it becomes 
filled with air bubbles. The mixture of corpuscles and serum 
may best be accomplished by first giving the receptacle a cir- 
cular motion and finally stirring briskly with a glass rod or meas- 
uring pipette which is filled while stirring the blood. 
Pipette for Measuring Blood.—The pipettes are made of milli- 
meter glass tubing calibrated to contain 0.05 ce. and 0.10 ce. The 
pipettes are easily made in any laboratory from straight tubing, 
and require no blowing, the point being rounded off on an emery 
wheel. In this way time and expense are saved, since pipettes 
