172 MICROMETRY AND BLOOD PREPARATIONS 



The first drop of blood which exudes should be taken up on the paper 

 of the Tallquist hsemoglobinometer, using subsequent ones for the blood 

 pipettes and smears. If it is necessary to make a complete blood ex- 

 amination, it is rather difficult to draw up the blood in the pipettes, 

 dilute it, and then get material for fresh blood preparations and films 

 without undue squeezing, which is to be avoided. Of course, fresh 

 punctures can be made. Ordinarily, complete blood examinations are 

 not called for. It is only a white count or a differential count or 

 an examination for malaria that is required. 



As a practical point it is very rare that a red count is indicated. There is one 

 point not sufficiently recognized by physicians and that is that a call for a routine 

 blood examination is not apt to be as carefully conducted as one calling for a specific 

 feature. Without disparaging the necessity of routine examinations of urine as 

 well as blood it is a fact that the internist who knows what he wants gets better 

 results from the laboratory man. 



HEMOGLOBIN ESTIMATION. 



The most accurate instrument for this purpose is the Miescher 

 modification of the v. Fleischl haemoglobinometer. 



The magenta-stained glass wedge for comparison with the diluted blood is similar 

 in each instrument, but by the use of a diluting pipette accurate dilutions are possible 

 in the Miescher. There are two cells provided one 12 millimeters high, the other 

 15 millimeters; the idea of this being to enable one to make separate comparisons 

 and to select the central part of the glass- wedge scale, where comparison is more 

 accurate than at the ends. As these cells contain columns of diluted blood propor- 

 tionately as 5 to 4, we should have similar readings when we multiply the reading 

 on the scale with the 15 mm. cell by 4/5. 



The mixing pipette is graduated with the marks 1/2, 2/3 and i/i the first 

 giving a dilution of i to 400 (when the diluent, 3,0.1% soda solution, is drawn up to 

 the mark above the bulb) the second of i to 300 and the last of i to 200. 



Artificial light preferably from a candle is necessary. There is a table accom- 

 panying each instrument which shows the value for that particular instrument in 

 milligrams per liter of haemoglobin for any reading obtained on the scale. 



The apparatus is expensive, requires considerable time and care in the making 

 of estimations, and is exclusively an instrument for a well-equipped laboratory. 



Sahli's Haemometer. A simple and apparently very scientific 

 instrument which has been recently introduced is the Sahli modifica- 

 tion of the Gower haemoglobinometer. Instead of the tinted glass, or 

 gelatin colored with picrocarmine to resemble a definite blood dilution, 

 Sahli uses as a standard the same coloring matter as is present in the tube 

 containing the blood. By acting on blood with ten times its volume of 



