176 
MALARIA 
between certain phenomena which precede 
the rigor and the reaction or “haemoclasis” 
resulting from the inoculation of certain 
foreign substances. These include a low¬ 
ered arterial tension, leucopenia, diminu¬ 
tion in the number of erythrocytes and 
changes in coagulability of the blood. 
Renewed Clinical Activity 
Malarial infections, even when untreated, 
frequently, almost characteristically, pro¬ 
duce a series of clinical attacks separated 
by varying periods of quiescence. The first 
period of clinical activity following inocu¬ 
lation is known as the primary attack while 
the subsequent periods of secondary activ¬ 
ity, depending upon the length of the 
interval between the termination of the 
primary attack and the reactivation, are, 
following James, variously designated as 
(a) recrudescence—renewed activity 
within 8 weeks, (b) relapse—renewed ac¬ 
tivity within from 8 to 24 weeks, and (c) 
recurrence — renewed activity after 24 
weeks. 
There is no certain criterion by which 
the end of the primary attack may be recog¬ 
nized. We have arbitrarily considered that 
the beginning of a quiescent interval at 
least equal to the suppression of two com¬ 
plete consecutive parasite cycles (5 days) 
marks its end. We have, however, reasons 
to believe that with vivax infections at least 
an interval of three weeks would be a surer 
criterion. 
The duration of an uninterrupted pri¬ 
mary attack in a highly susceptible person, 
as well as the duration of the quiescent in¬ 
tervals before secondary clinical activity, 
varies with the species of parasite, while the 
likelihood of secondary attacks may vary 
with the strain. Thus we have observed 
vivax patients to have an unbroken series 
of quotidian or tertian paroxysms for more 
than 60 days, quartan patients to have 
quotidian, double quartan or simple quar¬ 
tan paroxysms for more than 300 days, and 
falciparum patients a course lasting for 
more than 35 days. In vivax infections 
we have not observed secondary attacks 
when the primary attack exceeded 48 days 
in duration, while they may occur in fal¬ 
ciparum infections in which the primary 
attack attains the maximum duration. 
These infections can maintain themselves 
in a chronic latent condition for indeter¬ 
minate periods following the permanent 
cessation of clinical activity. It is impos¬ 
sible to assign even approximate limits to 
their persistence, but it appears that it is 
shortest for falciparum and longest for 
quartan, which latter may persist for sev¬ 
eral years. It is important to note that 
artificially induced infections in human 
subjects do not exhibit the chronicity which 
characterizes the naturally induced infec¬ 
tions, although artificially induced avian 
infections appear to present a chronicity 
comparable to the naturally induced. The 
significance of this will be considered later. 
The frequency with which secondary 
clinical activity has been observed subse¬ 
quent to natural inoculation is shown in 
Table X. 
From this table it is seen that secondary 
attacks occur in a considerable proportion 
of patients whose primary attacks termi¬ 
nate spontaneously. They are very nearly 
TABLE X 
Frequency op Secondary Clinical Activity in 
Relation to Manner of Termination of 
the Primary Attack 
Per cent with secondary attacks 
Termination 
of primary 
attack 
P. vivax strains 
P. falciparum 
strains 
McCoy Mada ' 
J gascar 
Vari- Vari¬ 
ous ous 
Spontaneous, 
without sub¬ 
sequent treat¬ 
ment . 
58.0 
42.8 . 
Induced, but 
without sub¬ 
sequent treat¬ 
ment . 
100.0 
85.6 . 
Induced, with 
subsequent 
treatment. 
25.0 47.4“ 
8.3 80.6b 
“James, S. P. (1931). b James, Nicol and 
Shute (1932). Includes naturally and artificially 
inoculated patients. 
