DIAGNOSTIC APPLICATIONS OF THE BLOOD-COUNT 2/3 



DIAGNOSTIC APPLICATIONS OF THE BLOOD- 

 COUNT AS A WHOLE 



In this chapter a brief outline of the chief practical applica- 

 tions of the blood-count will be given, with especial reference 

 to cases where it is of use in the discrimination between two 

 diseases which are difficult to distinguish clinically. 



HAEMORRHAGE. After a severe haemorrhage there is at first 

 no alteration of the blood ; the total volume is diminished, but 

 the part that remains is normal. In a very short time, how- 

 ever, fluid is absorbed from the tissues so as to make up the 

 normal volume, and in consequence the red corpuscles and 

 haemoglobin fall in the same proportion. With this there is 

 usually a leucocytosis, high figures (20,000 or more) being 

 sometimes reached ; do not forget this in dealing with a blood- 

 count in a patient who has recently had a haemorrhage. As 

 the process of regeneration continues, the improvement shows 

 itself first in an increase of the red corpuscles, so that the 

 colour-index falls slightly (to about 0*9). 



The anaemia from repeated haemorrhages is one of the 

 varieties of secondary anaemia. 



SECONDARY ANEMIA. This term is used for anaemia which 

 is due to any definitely recognized cause haemorrhage, mal- 

 nutrition, sepsis, intoxications (e.g., lead-poisoning), etc. 

 that is to say, it includes all cases of anaemia except those of 

 unknown pathology, such as chlorosis and pernicious anaemia. 



In secondary anaemia there is a reduction of red corpuscles 

 to an extent dependent on the potency and continuance of the 

 cause, and a slightly greater reduction of the haemoglobin, so 

 that the colour-index is lowered. It does not usually fall 

 below 07, and O'8 may be taken as a fair average. Anything 

 below this is rarely met with apart from chlorosis. The red 

 corpuscles are usually practically normal in appearance; nor- 

 moblasts are rare, and their presence is a good sign. 



The leucocytes, especially the polynuclears, are usually 

 slightly increased, and this is the chief or only means of dis- 

 tinguishing a secondary anaemia with low colour-index from 

 chlorosis, in which the leucocytes are normal or reduced. 



PERNICIOUS ANAEMIA. The feature which usually first 

 raises suspicion of pernicious anaemia is the high colour-index. 



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