246 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



The number of red corpuscles per cubic millimetre is 

 increased for a short period in any condition in which the total 

 volume of the blood is diminished by loss of the fluid portion 

 of the blood e.g., in severe diarrhoea. 



This fact is occasionally of diagnostic value. For example, 

 the red corpuscles appear more numerous in typhoid fever, 

 especially in the earlier stages of the disease : the figure may 

 exceed 6,000,000. Later in the disease a fall takes place, 

 though it is never very great, and if in a continued fever the 

 red corpuscles are less than 3,000,000, the diagnosis of typhoid 

 is unlikely. This is very different to what happens in malaria, 

 where there is great and progressive destruction of the red 

 cells, and a figure below 2,000,000 very common. This may 

 be of value in diagnosis in cases where the parasites cannot 

 be found, and Widal's reaction fails or cannot be tried. 



On the other hand, care must be taken not to mistake this 

 concentration of the blood for an actual improvement e.g., 

 if in a case of septic infection, puerperal fever, etc., the num- 

 ber of reds shows a sudden rise, the question of whether the 

 blood has been concentrated by profuse diarrhoea, sweating-, 

 etc., must be inquired into before the findings raise hope of 

 speedy recovery. Mistrust all results showing an increase 

 of more than 100,000 red corpuscles a day. Such rapid im- 

 provement does occur, but is unusual. 



The red corpuscles are also very numerous (up to 

 10,000,000) in congenital cardiac disease with cyanosis, and 

 as an obscure primary condition, and in venous stasis from 

 mitral disease or any other cause. 



A decrease of the number of red cells indicates anaemia, 

 and the numbers may be taken as a criterion of the degree of 

 anaemia present. But this is not so accurate a test as the 

 percentage of haemoglobin, since it is the quantity of this 

 substance that is of importance, the number of parcels into 

 which it is divided being of comparatively little moment. The 

 grade of anaemia, therefore, should be expressed by the per- 

 centage of haemoglobin, not by the number of corpuscles. 

 This is of some importance, since in the cases of typhoid 

 fever referred to above the haemoglobin is usually slightly 

 lowered, showing that there is anaemia, even where the num- 

 ber of corpuscles is abnormally high. 



In the diagnosis of the nature of an anaemia the enumera- 



