ESTIMATION OF THE AMOUNT OF HEMOGLOBIN 231 



turn on the gas, and allow it to run into the tube for some 

 time. When the comparison-tube is rilled with gas remove 

 it, close it quickly with the finger, and shake gently for a 

 minute or two ; if you wet your finger with the diluted blood, 

 wipe it off carefully on to the top, so as to avoid loss. 



The remaining steps are again like those in Cowers' hsemo- 

 globinometer, but with this difference: that you are a com- 

 paring two solutions of the same substance. These are very 

 easy to match, and the exact quality of the light does not 

 matter, so that the method may be used by any artificial light. 



I find it convenient to saturate the water in a bottle with 

 CO by bubbling coal-gas through it for some minutes. The 

 haemoglobin is then converted into CO haemoglobin in the 

 process of dilution, no further gassing is necessary, and the 

 procedure is exactly like Cowers' in all respects. The solu- 

 tion will keep for a day or two if well stoppered. 



SAHLI'S H^MOGLOBINOMETER. Here the standard consists 

 of a solution of acid haematin in glycerin and water, and has 

 a brown colour. To use it it is necessary to convert the 

 haemoglobin of the blood to be tested into acid haematin, so 

 that (as in Haldane's method) two solutions of the same sub- 

 stance are compared. A dilute solution of HC1 (about 

 i per cent., the exact strength being immaterial) is required. 

 This is placed in the graduated tube, and the measured 

 amount of blood added: this soon turns brown, but half an 

 hour or so should be allowed to elapse before the final step 

 is carried out, as the solution gradually darkens. Then the 

 further dilution is carried out, with water or dilute acid, until 

 the depth of the colour exactly matches the standard. 



This method is the most convenient for clinical work, and 

 is sufficiently accurate. 



OLIVER'S H^MOGLOBINOMETER differs from that of Cowers' 

 in that the degree of dilution is constant and the colour of 

 the diluted blood is read off by comparison with a series of 

 carefully graduated standards. It consists of (i) a capillary 

 glass tube with thick walls and ground ends, one of which is 

 flat and the other pointed : this tube is mounted in a metal 

 handle, the other end of which serves as a stirrer (Fig. 45, r); 

 (2) a small cell with an opaque white bottom, and provided 

 with a cover-glass which has a slight bluish tint (?); (3) a 

 series of twelve coloured glass discs mounted over an opaque 



