80 
PRINCIPLES OF BACTERIOLOGY 
being the microphages and the lymphocytes the macro¬ 
phages of Metchnikoff) increased. 
This increase or decrease of neutrophiles or lympho¬ 
cytes is independent of the total leucocytosis or leuco- 
penia—that is, one may have an increase of total number 
of leucocytes and a decrease of any given kind of leu¬ 
cocytes, or one may have a decrease of total number 
of leucocytes with an increase of any one or more types 
of leucocytes; for example, one may have 15,000 leu¬ 
cocytes and only 50 per cent neutrophiles or 10 per cent 
lymphocytes, or one may have 5,000 leucocytes and 80 
per cent neutrophiles or 50 per cent lymphocytes—such 
increase or decrease in the percentages of the different 
types of leucocytes in the presence of the opposite con¬ 
ditions of the total leucocytes is called relative increase 
or decrease: if for example one has leucocytosis of 
15,000 and only 50 per cent neutrophiles (instead of 
70 per cent) this decrease is relative (because there 
really is an absolute increase of neutrophiles—50 per 
cent of 15,000 being 7,500, whereas normally one has 
only 70 per cent of 8,000, which is 5,600) ; again if one 
has a leucopenia of 5,000 with 40 per cent (instead of 
20 per cent) of lymphocytes, this increase in lympho¬ 
cytes is only relative (since there really is an absolute 
decrease of lymphocytes, 20 per cent of 8,000 is 2,500, 
whereas 40 per cent of 5,000 is 2,000). 
It is of the greatest importance to determine the dif¬ 
ferential count, especially the percentage of neutro¬ 
philes, because while increase in the total leucocyte count 
gives us an idea of the protection or defense of the body, 
the increase of neutrophiles corresponds to the severity 
of the infection—the student should always remember 
this: total leucocytosis refers to protection , increase of 
neutrophiles refers to severity of infection . 
