GeorgeC. Low, ElizabethJ. O'Driscoll
1921 The Lancet  
221 of the cells was finished. At least two separate drops of each dilution were counted, both in the case of the differential method and in that of the Biirker counting chamber. The details of the experiment are given in the following table :-In the case of the differential method, an average of 360 nucleated cells and an average of 550 human red cells were counted in each drop, making a total of 910 cells per drop. In the case of the counting chamber method, on an average 1030 cells per drop
more » ... 030 cells per drop were counted. The average count for the two drops of the same suspension was in both cases taken as the figure representing the number of human red cells per cubic millimetre. Obviously, if it were possible to eliminate all errors of dilution, distribution, and enumeration, the final figures arrived at for each of the five dilutions would be identical. In an actual experimen t,however, identical results are not attained, and for this reason the average of the five is in both cases taken as the figure representing the actual number of red cells per cubic millimetre of the blood examined. The close correspondence between the results obtained by the two methods is striking. By the differential method it is found that the blood examined contains 5,386,750 red cells per cubic millimetre, while by means of the Biirker chamber it is found to contain 5,397,200 red cells, which gives a difference between the results obtained by the two methods of 10,450-i.e., 0'19 per cent. If we examine the percentage deviation of each count from the average this is found to be 1'25 per cent. in the case of the differential method, while it is 1'46 per cent. in the case of the counting chamber method, although in the latter case a larger number of cells is counted. Furthermore, if we calculate the percentage deviation for the figures obtained from the counting of each individual drop by both methods, it is found to be 2'29 per cent. by the differential method and 2'46 per cent. by the counting chamber method. Conclus'ions. By careful procedure, and by counting the numbers of cells indicated above, it is evident that the method discussed in this paper yields extremely accurate results, which compare more than favourably with the results obtained by the use of a counting chamber. It furthermore possesses the following distinct advantages: (1) It can be used with equal facility for counting . erythrocytes, leucocytes, and bacteria; (2) it does away with the use of a costly counting chamber; (3) it is quicker and less fatiguing to the eye. CENTRAL MIDWIVES BOARD FOR SCOTLAND.-At a meeting of the Board held in Edinburgh, Sir J. Halliday Croom in the chair, the Viscountess Novar took her seat as a member of the Board. Sir Halliday Croom, in a valedictory address on his retirement from the Board, thanked the members for the loyal support he had received as Chairman, and referred to the pleasant and harmonious way in which the work had been carried out. On the motion of Dr.
doi:10.1016/s0140-6736(01)23323-6 fatcat:npq62tsuhnerfh4d2r3xsm65da