ESTIMATION OF HEMOGLOBIN 13 



over the shoulder while making the comparison. When they 

 are of the same tint the hemoglobin value is read from the dilut- 

 ing tube, reading at the middle of the meniscus. As the readings 

 on the lower part of the scale are not accurate, it is advisable to 

 use two pipettes of blood for low percentages, dividing the result 

 obtained by two. 



Gower's hemoglobinometer is used extensively, though not 

 so extensively as a few years ago. A decided disadvantage is 

 that the tint of the standard solution is not permanent, becoming 

 darker after a time. It does not give the hemoglobin value closer 

 than about five per cent. The instrument is not enough more 

 accurate than Tallqvist's to make it advisable to use. 



There are modifications of Gower's hemoglobinometer in which 

 the standard solution of picrocarmine is replaced by modified 

 hemoglobin, permanent solutions it is claimed. This is an ad- 

 vantage in that the same things are compared since the blood is 

 modified in the same manner as the standard solution. As the 

 same substances are compared any kind of light may be used. 



In Haldane's modification the standard tube contains CO 

 hemoglobin. The sample of blood is treated, before making the 

 comparison, with illuminating gas. Some of the blood may easily 

 be lost, bubbles form and illuminating gas is not always available 

 clinically. 



In Sahli's modification the standard solution is hemoglobin in 

 glycerin. The blood to be tested is treated with a one-tenth normal 

 HC1 solution. Sahli's standard solution is claimed to be perma- 

 nent; but on standing for some time the hemoglobin sometimes 

 settles and cannot be made a uniform solution again. 



Dare's hemoglobinometer. — The instrument consists essen- 

 tially of a capillary pipette and a standard color scale representing 

 the hemoglobin values from 10-120. The pipette is composed of 

 two glass plates, one transparent and the other white which has a 

 depression of measured depth ground in one end so that when the 

 plates are clamped in the holder the depression forms a capillary 

 chamber which fills automatically when either of the three sides 

 is touched to a drop of blood. The standard color scale consists 

 of two prismatic glass plates tinted to give the color of undiluted 

 blood by candle light and arranged in the form of a semicircle, 

 the outer part of which increases in depth of color. The percent- 



