VII.] 



ESTIMATION OF HAEMOGLOBIN. 



2. With a lancette or needle puncture the skin of the finger at the edge of 

 the nail. 



3. With the pipette suck up exactly 10 c.mm. of blood. Mix this blood with 

 the .5 c.cm. saline solution, and suck part ot the latter several times into the 

 capillary tube, so as to re- 

 move every trace of blood 



from the pipette. Mix the 

 fluids thoroughly. Care- 

 fully cleanse the pipette 

 with water. 



4. Pour the mixture into 

 the reservoir (r) of the in- 

 strument. Gradually rotate 

 the inner tube, and as the 

 two glass discs separata, 

 the fluid passes into the 

 space between them. 



5. In a dark room light 



t 



FIG. 38. Showing how cd fits into ab. zz. Plates of glass 

 closing the ends of ab and cd; other letters as in 



a stearin candle, place if at 

 a distance of i metres, and, taking the instrument in the left hand, bring 

 the open end of the tubes to the right eye. With the right hand rotate the 

 inner tube to vary the thickness of the column of fluid, and so adjust it 

 until the outlines of the upper three-fourths of the flame can be distinctly 

 seen through the stratum of fluid. Vary the position of the inner screw so 

 as to determine accurately when this occurs. Read off on the scale the 

 thickness of the stratum of fluid. 



Graduation of the Instrument as a Cytometer. In this instrument the 

 graduation is obtained from the thickness of the layer of blood itself, and the* 

 amount of hemoglobin is calculated directly from the thickness of the layer 

 of blood which is necessary to obtain a certain optical effect, viz. , through the 

 layer of blood -corpuscles to see the outlines of a candle- flame placed at a 

 certain distance. 



From a number of investigations it appears that in healthy blood the out- 

 lines of the flame of a candle are distinctly seen through a layer of the mixture 



of blood mm. in thickness. 

 100 



Let the number no correspond to i, or to 100 parts of haemoglobin ; then 

 it is easy to calculate the relative value of the subdivisions of the scale on the 

 tube of the instrument. Let g = the degree of the scale for normal blood ; 

 </', that for the blood being investigated ; e, amount of haemoglobin in the 

 former ; and e', the amount sought for in the latter. 



Assuming that the product of the quantity 01 haemoglobin and the thickness 

 of the stratum of blood is constant, so that 



Then we have 



Let us assume that the blood investigated gave the number 180; then 

 using the above data, we have : 



, IQOX no n,ooo , 

 ~i8o ' 180 



