THE JOURNAL OF PHARMACOLOGY. 



123 



island. We find them forming small squares, sixteen such forming a large 

 square enclosed by three lines on each side. "We now proceed to count the 

 corpuscles by counting those totally within a small square and those touch- 

 ing or overlapping two sides of the square, as the right and lower sides, 

 and proceed with other squares in same way. We thus avoid counting a 

 corpuscle twice and failing to count one. We should count about one 

 hundred squares, then clean the slide and take another drop, and count 

 one hundred more, in all about two hundred squares. As each square is 

 1-400 millimeter square and the distance from the island to the cover- 

 glass .1 millimeter, we have in each square the number in 1-4000 cubic 

 millimeter. So, if we take the total number of corpuscles counted, divide 

 by the number of squares, we have the average number in one square, and 

 multiply by 4,000 we have the number in one cubic millimeter of diluted 

 blood; again multiply by the amount of dilution and we have the number 

 in one cubic millimeter of blood. The white blood corpuscle counter is 

 constructed upon the same principle, the dilution 2 generally being 1 :10, 



2 A DILUTING SOLUTION WHICH STAINS THE LEUCOCYTES IS TOISSON'S. 



in 1 Methyl violet, 5 b 0.025 



Neutral glycerin 30 



Distilled! water 80 



(b) Sod. chlor .' 1. 



Sod. sulph 8. 



Distilled water 80 



Mix (a) and (b) and filter. 



so it needs no further explanation. The technique seems, at first sight, 

 simple, but its practical application is fraught with many petty annoy- 

 ances. We may admit air into the tube; we may, especially when the co- 

 agulability of the blood is rapid, as in chlorosis, owing to slowness in ma- 

 nipulation, get coagulated inasses in the tube; we may draw the blood too 

 far beyond the stopping mark; in fact, we may encounter many failures 

 until practice in the use of the instrument lessens the chance of a mistake. 

 Each one of these errors means a thorough cleaning of the instrument — 

 a tedious procedure. We first wash out with water, then with absolute 

 alcohol, then with ether, and then dry, which is accomplished easiest with 

 air blown through the tube from an atomizer bulb. Care must be taken 

 to have the tube thoroughly clean, free from dust, and perfectly dry be- 

 fore using it. A modification of the red blood corpuscle counter by Prof. 

 Miescher, of Basel, is used by me in preference to the tube, because it 

 certainly lessens the chances of error. You will notice we have three stop- 

 ping places — 1-200, 1-150 and 1-100. If we go beyond the first, we may 

 go on and try for a landing at the second, that is, 1-150. There are also 

 two little, lines above and below each station, which helps us more easily 



