2l8 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



THE INVESTIGATION OF THE MORPHOLOGY OF 

 THE LEUCOCYTES AND RED CORPUSCLES 



To study the morphology of the leucocytes and red corpuscles 

 it is necessary to prepare thin and even films of the blood, and to 

 submit them to appropriate methods of staining. 



Method of Preparing Films— I. With Cover-glasses. 



This is the best method for ordinary purposes, and, if the 

 instructions are carried out exactly, is a very easy one. 



Requisites. — i. Perfectly clean cover-glasses. They should be 

 cleaned by one of the methods described on p. 32, and kept in 

 spirit. Immediately before they are required for use they must 

 be removed with a clean pair of forceps and dried with an old 

 and soft handkerchief. They may then be passed rapidly through 

 the flame, and allowed to cool. 



I prefer No. 2 cover-glasses for this examination, as much 

 better films are made on them than on thin ones, which are 

 liable to bend under the powerful suction exerted by the capillary 

 attraction of the drop of blood when spread out thin. 



2. A needle for drawing blood. 



(3. A platinum loop having a diameter of about -^-^ inch is 

 sometimes useful, especially to a beginner.) 



Rub the patient's ear or finger thoroughly with a piece of lint or 

 a towel, so as to make it hyperasmic. Prick it, and wipe away 

 the first drop of blood. Then allow another drop to exude ; if 

 necessary, you may squeeze it a little. 



Take a cover-glass between the first finger and thumb of the 

 left hand, holding it by the opposite angles, and take another 

 between the first finger and thumb of the right hand, holding it 

 by adjacent angles (Fig. 46). 



Touch with the upper surface of the cover-glass in your left 

 hand the drop of blood on the patient's skin, so as to remove a 

 very small droplet. This is the most difficult step: you must 

 not get too much or too little blood, otherwise the films will be 

 useless. It is advisable to avoid letting the cover-glass touch the 

 patient's skin. 



Now put the right-hand cover-glass over the left-hand one, the 

 centres coinciding ; lower the upper (right-hand) one until the 

 droplet of blood just touches it, and then let go (Fig. 47). 



