GENERAL BACTERIOLOGY 
81 
The following combinations may, therefore, be 
present: 
1. Leucopenia (e.g., 5,000) or slight leucocytosis (e.g., 
10,000) with high percentage of neutrophiles (e.g., 90 
per cent)—this is the most unfavorable combination, as 
it means low protection against a very severe infection. 
2. High leucocytosis (e.g., 20,000) with high percent¬ 
age of neutrophiles (e.g., 90 per cent); this is not quite 
as bad, as it means a strong protection against a very 
severe infection. 
3. Leucopenia (e.g., 5,000) or low leucocytosis (e.g., 
10,000) with a low percentage of neutrophiles (e.g., 70 
per cent)—this shows a weak protection against a weak 
infection. 
4. High leucocytosis (e.g., 20,000) and a low percent¬ 
age of neutrophiles (e.g., 75 per cent)—the most favor¬ 
able combination, as it means a very strong protection 
against a mild infection. 
Walker has summarized the various combinations into 
what is known as the Walker’s Index: he regards the 
normal leucocyte count as 10,000, and the normal per¬ 
centage of neutrophiles as 70 per cent; he further says 
that so long as the neutrophiles (the index of the severity 
of infection) increases 1 per cent for every 1,000 of the 
total leucocyte count (the index of protection), there is 
no cause for alarm; in other words if total leucocyte 
count is 10,000, percentage of neutrophiles may be 70; 
if total leucocyte count is 15,000, percentage of neutro¬ 
philes may be 75; if total leucocyte count is 20,000, 
percentage of neutrophiles may be 80; if total leucocyte 
count is 25,000, percentage of neutrophiles may be 85; 
if total leucocyte count is 30,000, percentage of neutro¬ 
philes may be 90; and so forth, without causing any 
alarm 
