DIAGNOSTIC APPLICATIONS OF THE BLOOD-COUNT 225 



tubercle and malaria, but is of diagnostic value in distinguishing 

 typhoid from septicaemia, in which case there may be no excess 

 of leucocytes, but there is usually a relative excess of polynuclears. 

 The number of leucocytes in typhoid is of some value in prog- 

 nosis ; the lower the count, the more severe the case, though to 

 this rule, as to all others in blood-work, there are exceptions. 



In the later stages of the disease the diagnosis is best made by 

 Widal's reaction. 



Complications. — Here the condition of the patient must be taken 

 into account ; a complication («.§■., perforation) which causes a 

 rapid and marked leucocytosis in a patient who has not been 

 greatly enfeebled by a long and severe illness may cause no 

 increase, or even a diminution, in an exhausted subject. If this 

 rule is forgotten, the indications from the blood-count may be 

 unjustly stigmatized as misleading. 



Perforation. — There is a rapid increase of leucocytes, which is 

 said to occur in half an hour ; the total number may be 15,000 or 

 more. In a patient who is not greatly exhausted this is a very 

 sure sign ; exceptions do occur, but are not frequent. 



Hamorrkage. — If a count has been made a short time previously, 

 a fall in the red corpuscles may be noticed in some cases, but does 

 not always seem to occur. There may also be slight leucocytosis ; 

 this is only of importance in that it leaves the diagnosis of 

 perforation or haemorrhage doubtful, though raising the pre- 

 sumption that one or other has occurred. As a rule it is not 

 high, and the more it rises above 15,000, the more likely is 

 perforation to be the cause. 



Pneumonia. — When it occurs early in the disease there is usually 

 a slight leucocytosis ; when it occurs later there may be none. 

 Do not exclude pneumonia, therefore, because of its absence. 



It follows from the above that a raised leucocyte count in 

 typhoid fever always points to a complication of some sort, but 

 does not necessarily indicate its nature. 



Pneumonia. — Here the results of blood examinations are 

 fairly constant, and of much value in diagnosis and prognosis. 

 In ordinary cases there is marked leucocytosis, due entirely to 

 an increase of the polynuclears, which may reach 95 per cent. 

 There is also moderate secondary anaemia. 



According to Ewing, who has had much experience on the 

 subject, the grade of leucocytosis is roughly proportionate to the 

 extent of the lesion. The following are his averages : 



