134 



Journal of Applied Microscopy. 



sterilized by lieat and may be thrown 

 away when once used. 



The part should be pricked sufficiently 

 deep to cause the blood to flow without 

 the need of much pressure. After press- 

 ing out a few drops, which are wiped 

 away with a clean, dry cloth, a relative- 

 ly small drop is pressed out and caught 

 near the edge of a cover-glass, held in 

 the ordinary cover-glass forceps. 



This is quickly placed, blood side 

 down, on another cover-glass, care being 

 taken to overlap the two covers, only 

 about one-half, and to keep their edges 

 parallel. The drop of blood instantly 

 spreads out between the two covers. 

 They are now quickly drawn apart, and 

 if the covers are thin and clean, a thin 

 film of blood will be found on them. 

 They are now placed aside, blood side 

 up, and allowed to dry. The spreading 

 of blood is greatly facilitated by the use 

 of a forceps which Ehrlich has suggested 

 for this purpose. 



Fig. 2. Ehrlich's cover-glass forceps, for 

 holding cover-glasses for securing thin 

 film of blood. 



The manner of using these forceps is 

 as follows: before taking up a drop of 

 blood on a cover-glass, as above di- 

 rected, a cover-glass is fastened in Ehr- 

 lich's forceps, near the end, and in such 

 a way that about three-fourths of the 

 cover project to the right of the forceps 

 when held in front of the operator. 

 ^The Ehrlich's forceps, with the cover- 

 glass properly clamped, is held in the 

 left hand, with the ordinary cover- 

 glass forceps held in the other hand; a 

 cover is picked up, a drop of blood is 

 caught on its under surface, near its 

 further edge, and it is now placed on the 

 cover held in the Ehrlich's forceps, care 

 being taken to overlap the two covers 

 only about half and to keeping their 

 edges parallel. The two cover-glasses 

 are now quickly drawn apart. 



The film of blood on the cover held in 

 Ehrlich's forceps is usually spread much 

 better than on the cover-glass drawn off. 

 The former is kept, while the latter may 

 be turned over and used again for 

 spreading the blood on another cover- 

 glass. Some eight to ten covers are 

 spread after this manner and placed 

 aside to dry. 



Two methods may be used for fixing 

 the blood on the cover-glass: 



1. It may be hardened in a solution of 

 equal parts of absolute alcohol and ether, 

 in which solution the cover-glasses with 

 the blood may remain about two hours: 

 in it they may, however, remain for twen- 



ty-four to forty-eight hours without in- 

 jury. The preparations are then taken 

 from the ether and alcoholic solution 

 and placed on filter paper until the fix- 

 ing fluid has evaporated, when they are 

 ready for staining. It is hardly neces- 

 sary to add that the ether and alcohol 

 solution should be well covered up while 

 in use, to prevent evaporation. It may 

 be kept in a well stoppered wide-mouth 

 bottle, and may be used over and over 

 again for the purpose of fixing blood 

 preparations. 



2. Ehrlich recommends the fixing of 

 blood preparation by heat. He has sug- 

 gested a very simple apparatus, shown 

 in Fig. 3, by means of which blood may 

 thus be fixed. 



It consists of a copper plate about 

 fifteen inches long, four wide, and one- 

 eighth inch thick. The copper plate is 

 heated at one end by means of an 

 alcoholic or gas flame. 



Fig. 3. Plate for heating blood prepara- 

 tions: a, copper plate; c, blood prepara- 

 tions; f, tripod. 



If then, at the end of fifteen minutes, 

 a moistened glass rod is passed over 

 the plate, beginning at the end away 

 from the fiame, a place will be reached 

 where the water begins to boil. This 

 region of the copper plate is looked upon 

 as having a temperature of 100° C. ; it 

 is represented by a dotted line in the 

 figure. The blood preparations (c.) are 

 placed on the plate (blood side up) be- 

 tween the flame and this imaginary line 

 (nearer the latter), and heated for a 

 time varying with the stain to be used. 



The blood preparations fixed after 

 either of the above two methods are to 

 be stained as follows: 



Haematoxylin and Eoslne. — Before 

 staining in haematoxylin and eosine the 

 blood preparations should be fixed in the 

 alcohol and ether solution for a period 

 of about two hours, or by heat, at a 

 temperature of 100° to 110° C. roughly es- 

 timated as above directed, for forty-five 

 to sixty minutes. They are stained in 

 Boehmer's haematoxylin solution (men- 

 tioned in one of the former articles of 

 this series) for fifteen to twenty min- 

 utes. This is best done by spreading the 

 desired number of the fixed prepara- 

 tions, blood side up, over the bottom of 

 a flat dish and pouring over them 



