OF REICHERT's HiEMOMETER. 11 



and without any preceding compression, or binding of the finger, 

 as is usually done, it should be wounded by a slight prick with a 

 sharp needle. Then by a slight pressure above the little wound 

 a drop of blood is secured. This drop of blood is taken up with 

 one of the open ends of an automatic blood pipette, a small 

 capillary tube about 8 mm. in length, bound about in the centre 

 by a tiny wire, and of definite capacity (6 J cubic mm.). The 

 filling of the automatic blood pipette is considerably facilitated 

 and accelerated by holding it horizontally, instead of perpendic- 

 ularly ; that is, it is dipped sideways into a drop of blood. 



Since every trace of blood that clings to the exterior of the 

 tube is to be considered a serious defect, it is necessary to smear 

 the pipette with something of a fatty nature. This is best done 

 by keeping it in a leather case, lubricated with tallow. As soon 

 as the pipette is full the outer surface should be carefully examined. 

 If a speck of blood is found there, it must instantly be removed, 

 or before it has time to dry. This is done by means of a strip 

 of filtering paper or absorbent cotton. The blood is then much 

 more fully and easily absorbed when the exterior of the glass is 

 coated with an oleaginous substance. Care should be taken that 

 the column of blood ends at both extremities, on the same level 

 with the glass tubes, and neither with retiring nor with bulging, but 

 with even extremities. If it should be necessary to use filtering 

 paper or wadding to remove the blood from the exterior of the 

 pipette, care should be taken that these substances do not 

 approach too closely to the extremities of the blood column, in 

 order to avoid a meniscus. 



Even before these instructions are carried out, the various 

 parts of the Haemometer should be examined to insure perfect 

 cleanliness, and a perfect condition of the apparatus. The com- 

 ponent parts may then be arranged. The frame upon which the 

 red glass wedge reposes must be joined to the wing on the lower 

 side of the table slab, through which it finds its guidance. More- 

 over, the comparing vessel must be inserted into the opening 

 designed for it in the table slab, and so placed that the 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 dis- 



