226 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



Average Leucocytes. 



1 lobe affected 20,000 



2 lobes „ 22,700 



3 „ „ - - - 25,000 



4 >, >. : 27,000 



But higher counts, often much higher, are frequently seen. 



These figures serve to exclude typhoid fever, tuberculosis, 

 acute tuberculous pneumonia, and influenza, which do not cause 

 leucocytosis ; a true lobar pneumonia implanted on the latter 

 raises the leucocyte count, a lobular one does not. 



In a few cases of pneumonia there is no leucocytosis, but these 

 hardly detract from the value of the sign. They are (i) very 

 mild cases, and (2) very severe ones, usually rapidly fatal, in 

 which the system fails to react to the infection ; the iodine 

 reaction of the leucocytes is well marked in these. A low count 

 in pneurrjonia, therefore, may be a good or bad sign : which it is 

 can be told by a glance at the patient. A moderate leucocytosis 

 which gradually declines is a bad sign in a case of any severity. 



As a rule the leucocytes fall to nearly normal at the crisis, 

 sometimes a little before ; in such cases the crisis may be pre- 

 dicted, and a sudden fall to normal after a week or so is of 

 very good omen. If the leucocytes remain up after a crisis it is 

 most likely to be due to empyema. 



Malaria. — Here, of course, the diagnosis should be made by 

 finding the specific micro-organism in the blood (p. 142). 

 Where this cannot be done the case may still be one of malaria, 

 and the blood-count may aid in the diagnosis. There is anaemia, 

 often coming on rapidly and attaining very low figures. There 

 is no leucocytosis, and according to many observers there is a 

 great increase in the large lymphocytes, which almost always 

 become more numerous than the small ones. This test is not 

 interfered with by the administration of quinine, which renders 

 the parasites difficult or impossible to find. 



Scarlet Fever and Measles. — In the former there is, except 

 in the very mildest cases, a marked leucocytosis ; in the latter the 

 blood is normal in the absence of pneumonia or other complica- 

 tions. In scarlet fever the leucocytes range from 10,000 to 40,000, 

 and according to some authors the prognosis is very bad in cases 

 showing more than 30,000 ; there is an excess of polynuclears 

 (80 to 90 per cent.), which is very noticeable in children, where 

 there is usually a high proportion of lymphocytes. 



