12 CONCERNING THE RULES AND APPLIANCES 



tilled or pure spring water. The half above the wedge, called 

 " wedge half," is completely filled with water from the pipette, so 

 that the smooth surface which it forms above may be perfectly 

 level, forming neither a positive nor a negative meniscus. The 

 other, the blood half, is also filled with water from the pipette, but 

 only to about one-fifth, or at most, one-fourth of its capacity. 

 When this is done, the pipette out of which the vessel has been 

 filled, and which still contains a sufficient quantity of water to 

 complete the filling of the blood half, should be placed in a 

 horizontal position — /.<?., upon the brim of a goblet, so that the 

 water will not flow out of it. 



The pipette having been filled with blood, it should be brought 

 (in a horizontal position) under the water in the blood half of the 

 comparing vessel, when the little wire should be leaned against 

 the upper edge of the vessel, but not against the straight edge of 

 the partition wall, nor in either one of the corners at the end of 

 the same, but against the middle point of the curved edge of the 

 blood half. In this manner the little tube with the blood is made 

 to lie in the centre of the rectilinear chamber, which the partition 

 wall touches at the bottom of the vessel. 



The blood pipette should not be permitted to remain quietly 

 in that position under water, but a gentle motion should be 

 imparted by a judicious guidance of the little wire to which the 

 pipette is fastened ; that is, the little tube should be moved back- 

 ward and forward along its own axis as far as the dimensions 

 permit, and in this manner be moved to and fro over its fluid 

 contents. 



It is easily seen that these movements are directed to produce 

 a speedy solution of the contents of the tube with the surrounding 

 fluid. It is also readily seen how important it is that no time be 

 wasted in the proceedings following the taking of the blood, but 

 rather that all should be arranged as quickly as possible without 

 neglecting carefulness and exactness of execution. For the rest, 

 the caution not to work more slowly than necessary, refers only to 

 the manipulations. These motions are so easy and simple that 

 even an unskilled hand will need not more than one minute for 

 their execution. That much of time may pass without endanger- 

 ing the result in determining the amount of haemoglobin. 



