410 



5. Wash, for one minute in 



Water 50 c.c. 



Pot. permanganate, I % solution 2 drops. 



6. Wash in water five minutes. 



7. Stain with Romanowsky. 



For BreinPs method, which is more complicated, 

 vide Annals of Tropical Medicine and Parasitology, 

 Vol. I, No. 3. 



To MEASURE OBJECTS 



Method I. It is necessary to have (a) a scale 

 which is put into the eyepiece, and (b) a slide with a 

 millimetre (divided into hundredths) scale ruled on it. 

 Unscrew the top of the eyepiece and place scale (a) 

 inside, place the top on, and by holding the eyepiece 

 up to the eye see if the scale is in focus; if not, shift the 

 diaphragm on which it rests up or down until it is so. 

 Now focus scale (b) placed on the stage. Both scales will 

 now be seen at the same time. Proceed then to find 

 out how many divisions of the stage scale (b) one 

 hundred, or fifty (or any smaller number) divisions 

 of the eyepiece scale (a) cover. Let us suppose we 

 find that forty divisions of the scale (a) cover eight 

 divisions, i.e., rlny mm., i.e., Sop. Therefore one 

 division of the scale (a) is equal to 2ft. Then knowing 

 this leaving the eyepiece scale in position and removing 

 the stage micrometer let us now measure a blood cell, 

 and let us suppose we find it covers (using the same 

 lens and eyepiece as before) three divisions. As we know 

 that one division measures 2/^, the blood cell measures 

 6p. Having once determined the value of the eye- 

 piece scale for each combination of lenses and a definite 

 tube length (160 mm.), we require scale (b) no longer. 

 We simply place the scale (a) in the eyepiece, determine 



