200 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



the differential diagnosis of internal haemorrhage— ^.g'., in cases of 

 ruptured tubal gestation. 



4. In malaria there is a fall in the amount of haemoglobin, very 

 rapid and sudden in the early stages, and often marked, though 

 less rapid, in the later ones. The fall is often to an extent only 

 equalled in acute sepsis. This may be of much diagnostic value. 

 In typhoid fever and in the other diseases for which malaria may 

 be mistaken the anaemia is usually developed much more slowly, 

 if at all. 



ESTIMATION OF THE RED CORPUSCLES 



The best apparatus for the estimation of the number of 

 corpuscles (whether red or white) is the Thoma-Zeiss or Thoma- 

 Leitz haemocytometer. It is usually provided with two pipettes, 

 one for counting the red corpuscles and one for the leucocytes. 

 The latter is rarely used and need not be procured. 



Examine the pipettes. Each has a small bulb containing a 

 little glass ball, and a stem which is graduated into several parts 

 below the bulb, and has a single transverse graduation above it. 



The pipette intended for use in counting the leucocytes may be 

 distinguished by the fact that it has the figure 1 1 over the single 

 transverse graduation above the bulb. 



There are two forms of pipettes made for counting the red 

 corpuscles. In the one the stem below the bulb is divided into 

 ten parts, the upper one (nearest the bulb) being marked i, 

 and the middle one 0-5 (Fig. 41, S). In the other the same 

 portion of the stem is graduated into three portions numbered j-^g^, 

 •jig-, and -j-Jij ; the figure mentioned first is placed nearest the bulb. 

 These pipettes are used in the same way, and it is quite immaterial 

 which is obtained ; we shall describe the use of the first form. 



The rationale of the method is this : Blood is sucked up to one 

 of the divisions on the lower part of the stem, and then an inert 

 diluting fluid is drawn up to the single mark above the bulb, and 

 the two mixed by rotating the whole apparatus for a minute or 

 two. This gives us a dilution of blood of definite strength, the 

 exact amount of dilution depending upon the amount of blood 

 which was taken. Thus, if blood had been drawn up to the 

 figure I, we should have a dilution of i in 100; while if blood had 

 been drawn up to the figure 5, the dilution would be 0'5 in 100, 

 or T in 200, and so on. In the case of the other form of pipette 



