296 
MALARIA 
examine all persons in a community, tlie 
malariologist will generally limit his obser¬ 
vations to a sample, the size of which will 
depend on the total population, the time 
available, the trend of the current results 
and the character of the objective data 
sought (Boyd 1930a). Some malariologists 
will find it most practicable, for some par¬ 
ticular reason or personal preference, to 
limit themselves to observations on the inci¬ 
dence of parasites or splenomegaly alone 
or to consider both criteria together. If 
both are considered the observations should 
be made concurrently on the same indi¬ 
viduals. It should be remembered that the 
detection of parasites is more particularly 
indicative of infections recently active; the 
detection of splenomegaly, of a developing 
immunity. Hence the two criteria have a 
different significance. 
From the standpoint of practical em¬ 
ployment a spleen survey has wider useful¬ 
ness, especially if performed in the con¬ 
firming manner described, than a parasite 
survey, because it permits the examination 
of a larger sample with the further advan¬ 
tage that the results are immediately avail¬ 
able. The collection of blood smears from 
all persons examined, because of the 
greater time required per person, reduces 
the size of the sample, and its examination 
may delay the availability of the results 
for many months. 
Since schools include the younger age 
groups of both sexes, various races, and 
representatives of differing social status, 
they, are convenient centers in which to 
conduct the major investigations of the 
clinical survey. It is frequently unneces¬ 
sary to examine children over the age of 12, 
and many limit themselves to those under 
10. However, sometimes other age groups, 
including infants and adults, should be 
included; to reach them domiciliary visits 
will be required. 
The clinical survey should be made at, 
or immediately following, the period of 
greatest intensity of the disease. Once this 
period has been ascertained on the basis 
of history, mortality or morbidity data, or 
previous surveys, the examinations should 
be repeated if required, at the same time 
each year in order that the results may be 
comparable. 
The examination for splenomegaly is 
preferably made with patients in the re¬ 
cumbent position with knees flexed and 
abdomen bared. The examiner, standing 
on the patient’s right side, palpates lightly 
with the right hand which is held more or 
less at right angles to the costal margin. 
Two requisites are essential for successful 
examination: light pressure of the exam¬ 
iner with the hand flat upon the abdomen, 
and relaxation of the patient, associated on 
his part with full, deep, abdominal breath¬ 
ing. Thoracic breathing with tense muscle 
can prevent the detection of a spleen which 
otherwise would be readily palpated below 
the costal margin. 
The record should state the relative posi¬ 
tion of the lower border of the enlarged 
spleen. For this purpose Boyd’s classifica¬ 
tion of splenic enlargement has been found 
practical. His classification divides en¬ 
larged spleens into five groups, namely 
those palpable on deep inspiration (P.D.I.), 
and numbers 1, 2, 3, and 4. The ascending 
numbers indicate progressive degrees of 
enlargement, varying from No. 1 at the 
costal margin on normal inspiration, to 
No. 4, which extends below the umbilicus. 
No. 2 enlargement extends to any point 
lying from the costal margin to half-way 
to the umbilicus, and No. 3 from the former 
limit to the umbilicus. 
In order to demonstrate the extent to 
which the observed splenomegaly is attri¬ 
butable to malarial infection, it is desirable 
to take blood smears from each person with 
an enlarged spleen. Smears furthermore 
should be taken on a certain proportion 
(every second, third, fourth, etc.) of those 
persons presenting negative spleens. An 
analysis of the incidence of parasites 
among the persons with different spleen 
classes reveals the degree to which the ob¬ 
served splenomegaly is indicative of ma¬ 
larial infection. The number of those 
positive expressed as a percentage, how¬ 
ever, does not constitute a parasite index, 
although it may be estimated therefrom. 
