OF REICHERT'S HiEMOMETER. 13 



All depends upon the blood being mixed with a certain 

 quantity of water sufficient to dissolve it before it coagulates. 

 The shorter and broader the capillary, the more rapidly the blood 

 in the graduating capillary will mix with the surrounding water. 

 The volume of blood used for measuring will be determined with 

 greater exactness, the longer and narrower the graduating capillary 

 is. The most advantageous length and breadth of the blood 

 pipette is that which permits a rapid mixing of the blood and 

 water with a sufficient exactness in determining the volume. My 

 experience permits me to give a warning against the use of blood 

 pipettes, however well guaged, which are shorter than 7 mm., or 

 longer than 10 mm. Moreover, the edge of the blood pipette 

 must be rounded, must be allowed to shape itself in the flame, 

 but neither of the openings should be contracted nor narrowed. 



As soon as most of the contents of the blood pipette has 

 entered the water, the pipette should be withdrawn by the little 

 wire and held in a vertical position over the same, so that the 

 lower opening in the tube in the centre of the blood half of the 

 comparing vessel may be suspended several millimeters above the 

 surface of the liquid. Then, with the other hand, seize the drop- 

 pipette, which has already been filled with water, and allow drop 

 after drop to enter the upper end of the blood capillary. By this 

 means not only the contents of the blood capillary, even to the 

 very last traces of blood in the comparing vessel, are cleansed from 

 it, but the traces of blood clinging to the surface of the capillary, 

 and which were lifted from the comparing vessel, are again 

 washed back. 



If the drops which have detached themselves from the lower 

 end of the graduating capillary are observed, it may be seen how 

 rapidly the blood drops disappear, and how clear even the fifth or 

 sixth of these drops is. This is also shown under a careful examin- 

 ation by a graduating tube, perfectly clean both within and with- 

 out, perfectly smooth, and filled as well as washed with clear water. 

 Care must also be taken that no concretions or foreign substances 

 be on or between the coils of the wire which winds about the 

 blood pipette and serves as a handle. Only when all is declared 

 perfectly clean and free from blood, may the blood pipette be 

 wholly removed from the comparing vessel. 



