HiEMOGLOBIXOMETER. 151 



graduated tube stands at 90, then there is present 90 p - c - of 

 the normal quantity in the blood, e.g., of 14 P ' C ' 



Should the fluid reach the graduation 120 then there is 

 more by 20 pc - than the normal amount. 



Oliver's Hsemoglobinometer. (To be used in a darkened room.) 



(1) Automatic blood measurer, (2) mixing pipette, (3) the blood cell 

 and cover glass, the latter of low grade blue glass, (4) a set of 

 standard colour grades, (5) riders, (6) camera tube, (7) light 

 (Christmas candle), (8) bottle of antiseptic fluid, lancet, needle and 

 thread . 



Process : ( 1 ) Dry the blood measurer by drawing darning thread 

 through it with a needle. (2) Apply the point to the drop of blood 

 exuding from a pricked finger ; it will fill itself. There must be no 

 break in the column of blood. Dry the ends with a finger tip. 

 (3) Fill the mixing pipette with distilled water, and fit it on the 

 measurer. (4) Expel the blood into the blood cell by pressing water 

 through drop by drop. Stir with the handle of the measurer and 

 use it as a guide for adding the last drops required to fill the cell 

 exactly level with the edge. Do not fill to a convexity. (5) Apply 

 the cover, a small bubble should form, then the cell has not been 

 overfilled. (6) Place the blood cell by the side of the standard colour 

 grades under the camera tube, so that they are seen through separate 

 apertures at the bottom on looking down the tube. (7) Place the 

 lighted candle at about 10 cm equidistantly from the blood cell and 

 the standard. (8) Make the observation by looking through the tube 

 for not more than 10 seconds at a time, and in order to resensitise 

 the retina, if there is any fatigue, close the upper opening of the 

 tube with your finger, and glance for a few moments through the 

 green glass at the light before making another observation. Match 

 the blood tint exactly with one of the blood standards. Physiological 

 riders are supplied of nine degrees between standard grades. If the 

 blood tint lies between two, superpose riders on the lighter tint 

 until a match is obtained. To balance the glass of the rider a 

 colourless slip is placed over the cover of the blood cell. A descrip- 

 tion of this instrument is given because it rests upon (1) the 

 recognition of the irregular variation of the blood tint on dilution, 

 and (2) upon the employment of the delicate colour discrimination 

 method introduced by Mr. Lovibond, of the Tintometer Company, 

 which admits of many applications. A power of acutely discriminating 

 differences of tint is required in the observer. 



