NORMAL HJEMATOLOGY 145 



tain thickness with a revolving colored, wedge-shaped disk of glass. 

 The only preparation necessary is to clean and polish the glass plates 

 that hold the blood, and adjust them in their holder. 



Technique. Obtain a good-sized drop of blood in the usual man- 

 ner. Touch the edge of the plates to the drop of blood, and the space 

 between them will be filled with blood by capillary attraction. Place 

 the holder in its socket, adjust the telescopic tube and the lighted 

 candle, and make the reading in the same manner as with the Fleischl 

 instrument. A dark room is not necessary, but it is well to hold the 

 instrument toward some dark object as a background. 



D. Tallquist's Hsemoglobinometer. 



Tallquist's hsemoglobinometer consists of a chart or a paper on 

 which are twelve oblong, red-colored stripes, ranging from 10 to 

 120 per cent, in degree of color. The color of the stripe marked 

 100 is supposed to be the same color and shade as that of a piece 

 of filter paper in which there is normal blood. 



The other stripes vary from this as the numbers indicate. 



Appliances. Tallquist's hsemoglobinometer chart; fine Swedish, 

 tightly woven filter paper, and a glover's needle. 



Preparations. Take a large piece of light yellow-colored paper 

 and cut an oblong hole in its centre, not quite as large as one of the 

 colored stripes on the chart. Take a piece of the filter paper, at 

 least twice the size of the colored stripes, and cut a straight edge on 

 one side of the paper. Prepare the needle and ear as usual. 



Technique. Obtain the blood in the usual manner. Take the 

 prepared piece of filter paper and allow drop after drop of blood to 

 be absorbed into the paper until it is covered with blood over an 

 area as large as one of the colored stripes of the chart. Put on just 

 enough blood to saturate the paper, no less and no more. If there is 

 too little blood on the filter it will be white still on the under side. 

 If there is too much blood on the paper it will have a glistening sur- 

 face, and later will clot upon the paper. This must be prepared 

 quickly and very evenly and then compared with the colored stripes 

 of the chart at once. It will be noticed, when the blood is first put 

 upon the filter paper and is still fresh, that it has a glistening appear- 

 ance, but that it soon loses this and appears dull red for a few mo- 

 ments, and then it takes on a darker red appearance of clotted blood. 

 The time to take the reading is while it has the fresh, dull-red 

 color, just after the glistening surface has disappeared and before the 

 dry, darker red color comes. This gives only a few moments in which 

 to make the reading. Place the perforated paper on the colored chart 

 and place the filter paper with the blood right next to the oblong 

 perforation. The examiner must control his inclination to manu- 

 facture results. This is best accomplished by using the same method 



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