1890.] MICKOSCOriOAL JOUKISAL. 75 



projection of the vessel, as observed from above, may coincide with the 

 visible part of the free wedge lying beneath.' 



Both halves of the comparing vessel must be filled with distilled or 

 pure spring water. The half above the wedge, called " wedge half," 

 is completely filled with water from the pipette, so that the smooth sur- 

 face which it forms above may be perfectly level, forming neither a posi- 

 tive 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 fiow 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 th^ 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 judi- 

 cious guidance of the little w^ire to which the pipette is fastened ; that is, 

 the little tube should be moved backward 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 w^ith the surrounding fluid. It is 

 also readily seen how important it is that no time be wasted in the pro- 

 ceedings 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 w^ith- 

 out endangering the result in determining the amount of haemoglobin. 



All depends upon the blood being mixed with a certain quantity of 

 water sufiicient to dissolve it before it coag^ulates. The shorter and 

 broader the capillary, the more rapidly the blood in the graduating cap- 

 illary 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 sufiicient exactness in determin- 

 ing the volume. My experience permits me to give a warning against 

 the use of blood pipettes, however well gauged, which are shorter than 

 7 mm., or longer than lo 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 



