1524 Journal of Applied Microscopy 



A Few Remarks on the Technic of Blood Preparations. 



It is for those who have had the same difficulty as myself in mastering the 

 technic of dried and heated preparations of blood for clinical examination that 

 these remarks are intended. While I will not say that I have not sometimes 

 succeeded in getting beautiful preparations by the ordinary method of drying and 

 heating the cover-glass smears and staining with the Biondi-Ehrlich triacid stain, 

 I may say that to make a perfect slide in this way has been the exception, and 

 I have often had to try over and over again before accomplishing creditable 

 results. This I will not say is the fault of the method, but I imagine from 

 patient work that all are not able to acquire the requisite skill to make infallibly 

 a good mounting. My own results have been far from uniform. 



The method which I am now using is in no wise new, but it is the application 

 of well known principles that I would call attention to. With a little care and 

 at the expense of less time than the usual heat method employed, I have been 

 able to invariably get a good mounting. Instead of the cover-glass preparation, 

 the method of spreading the blood directly on the slide, as pointed out by Ewing 

 in his new work, is used. This consists of laying the slide to be smeared fiat on 

 the table, and picking up the drop of blood from the finger or ear on the end of 

 another glass slip and distributing it with a little movement along the edge of 

 the end of the slip and then bringing the end of this slide in contact with the flat 

 surface of the other at an angle of about thirty degrees and drawing it the 

 length of the slide with proper pressure to produce the required thickness of 

 film. The slide is then hastily placed in a Naples staining jar into which has 

 previously been put two or three drops of one per cent, osmic acid in 

 one per cent, chromic acid solution. It is allowed to stay in this vapor, the 

 cover having been placed on the jar, for from forty seconds to one minute. If 

 allowed to remain in the vapor too long, it will not take the stain. The object 

 is to allow it to remain just long enough that when removed the film will not 

 wash off when put under the tap of water. During the time the slide remains 

 in the jar the film will not dry, and when removed it should be dried carefully 

 over the lamp, and may be held as long as the hand will bear the heat. Without 

 any washing now, the film is flooded with an aqueous solution of eosin ( quite 

 strong ) and allowed to remain thus for from three to ten minutes. The time 

 will depend on the strength of the eosin solution and the fixation. It is then 

 washed under the tap for a considerable length of time, flooded with distilled 

 water and stained with a full strength solution of Mayer's haemalum for about 

 ten or fifteen minutes. It is then washed off in the hydrant and the tap water 

 allowed to run over it as long as desired. W^ith this method all cells are 

 characteristically stained, and everything is distinct and in good contrast. 

 Haematoxylin may of course be used for the nuclear stain instead of haemalum, 

 but it appears that the latter makes by far the most beautiful stain. 



As when one has once learned to distinguish the various elements of the 

 blood the oil-immersion lens is no longer necessary, there is no advantage in 

 using balsam as a rriounting medium, the slide may be allowed to drain and 

 be covered with a cover-glass and examined at once. 



While the above method does not fill all the requirements of the triacid stain 

 in pathological specimens, perhaps, it makes the differential count easier and 

 shows the different elements of the normal histology of the blood perfectly. 

 Chicago, 111. B. L. Rawlins. 



