HAEMOGLOBIN ESTIMATIONS 



201 



tube containing the blood. By acting on blood with 10 times its 

 volume of N/io HC1, haematin hydrochlorate is produced, which gives 

 a brownish-yellow color. In the standard tube, which is sealed, a 

 dilution representing i% of normal blood is used. 



To apply this test, pour in N/io HC1 to the mark 10 on the scale of the graduated 

 tube. Add to this 20 cu. mm. of the blood to be examined, drawn up by the capil- 

 lary pipette provided. So soon as the mixture as- 

 sumes a clear bright dark brown color, add water 

 drop by drop until the color of the tubes matches. 

 The reading of the height of the aqueous dilution 

 on the scale gives the Hb. reading. The tubes are 

 encased in a vulcanite frame with rectangular aper- 

 tures. This gives the same optical impression as 

 would planoparallel glass sides. 



The most accurate readings are obtained with arti- 

 ficial light in a dark room but almost as satisfactory 

 comparisons can be obtained with natural light from 

 a window. It is advisable to turn the ruled side 

 around so that one may match colors without being 

 influenced in his determination by the scale. 



The apparatus must be kept in a dark place as 

 strong light will change the color of the standard 

 tube. It is recommended that the N/io HC1 be 

 preserved with chloroform. 



Tallquist's Haemoglobin Scale. This is 

 a small book of specially prepared filter- 

 paper with a color-scale plate of 10 shades 

 of blood colors. These are so tinted as to 

 match blood taken up on a piece of the filter- 

 paper and are graded from 10 to 100. So 

 soon as the blood on the filter-paper has lost 

 its humid gloss, the comparison should be 

 made. 



FIG. 52. Sahli's haemo- 

 globinometer. (Greene.) 



This may be done by shifting the blood-stained piece of filter-paper suddenly 

 from one to the other of the holes cut in each shade the piece of filter-paper being 

 underneath the color plate; it is better, however, to match the colors with the blood 

 spot against the scale rather than behind a preparation. Grawitz prefers to cut the 

 stained spot from the filter-paper and place it directly on the color scale. 



At least a square centimeter of the filter-paper should be stained 

 by the blood. Daylight coming from a window to the rear or at the side 

 should be used in making the comparison. The error with this method 



