I26 THE JOURNAL OF PHARMACOLOGY. 



ties and an unconstant number of revolutions we get different results. 

 Again, in leukemia and anemias corpuscles of different sizes and shapes 

 would pack down differently from the healthy ones. This instrument is 

 intended to take the place of the Thoma-Zeiss counter, which we admit 

 is also not scientifically accurate, but the hematocrit does not seem to be 

 as accurate, and its liability to error is greater. I believe that the time 

 saved by its use and its reputed accuracy are not great enough to cause 

 us to discard the actual counting with the Thoma-Zeiss, or, better, with 

 Miescher's modification, above referred to. 



We now turn to the morphology of the corpuscle, which can be studied 

 in the fresh specimen, but many times to better advantage in the dried 

 films. In the preparation of blood films, as well as in all other hema- 

 tological researches, everything depends upon: — 



Technique. — To begin with, cover-glasses must be clean and free from 

 dust and oily material. We may do this by soaking in alcohol and ether, 

 carefully wiping with a clean old linen handkerchief, and then putting 

 them in a watch costal, which is placed in an oven and heated to 150 

 degrees Centigrade. Care should be taken not to handle with the fingers, 

 for the moisture will interfere with the even spreading of the blood. I 

 take the watch crystal from the oven and place another over it, and carry 

 the cover-glasses between the two watch crystals to the patient, then prick 

 the ear, and, taking one cover-glass in the forceps, I allow a small drop to 

 be touched at its apex by the centre of the cover-glass. I then place an- 

 other cover-glass over it, so that about one-sixteenth overlaps, then without 

 pressure draw the two steadily, evenly and quickly apart. If our cover- 

 glasses are clean, and proper care has been used in drawing them apart, 

 the blood will be evenly spread. If we have been careless the film will 

 have little holes or rings in it, and the whole will present an uneven ap- 

 pearance. Practice alone enables one to make well-spread films. We next 

 fix the films. Heat is recommended by Ehrlich, and is best if we use his 

 triple stain. We place the films in an oven, and run the temperature up 

 to 105 degrees Centigrade, withdraw the burner, and allow it to run up 

 to 115 degrees Centigrade:, then open the door and let it cool clown. We 

 may also fix in a mixture of alcohol and ether, equal parts, from fifteen 

 minutes to an hour, or even longer. If dealing with a marked anemia 

 better results are obtained by alcohol and ether. We have many methods 

 of staining, the important being eosin-hematoxylin. eosin-methylen blue and 

 Ehrlich's triple stain. The stain is simply spread on the film and washed 

 off in one to five minutes. It is well always to stain the same lenrvth of 

 time with the same stain. After washing we dry between filter papers and 

 mount in Canada balsam. 



We now take up the appearance of these stained films. 



