244 
MALARIA 
suitability of the normal host for the para¬ 
site, but as the initial infection is sup¬ 
pressed, it greatly increases and then rep¬ 
resents an acquired immunity. Various 
degrees of acquired immunity are gener¬ 
ally manifested from the suppression of 
the initial attack onward throughout the 
infection and during superinfection with 
the same strain. 
All evidence indicates that the death of 
parasites during both natural and acquired 
immunity is associated with phagocytosis. 
Several early observers, notably Golgi 
(1886c, 1888), Marchiafava and Celli 
(1887), Metehnikoff (1887) and Laveran 
(1889), studied the phagocytosis of ma¬ 
larial material and postulated that the 
process is functional in defense. Many 
subsequent workers, working oh human 
necropsy material, established beyond ques¬ 
tion that the macrophages, chiefly of the 
spleen, liver and bone marrow, and to a 
lesser extent of other sites, such .as the 
adrenal and around areas injured by the 
localizations of P. falciparum, as in the 
brain, phagocytose free and intracorpuscu- 
lar parasites and pigment. As evidence 
accumulated, some authors questioned the 
primary functional role of the phagocytes 
in suppressing the infection. Various 
theses were’ maintained, such as that the 
activity of the macrophages is limited to 
removing dead or effete material rather 
than vigorous viable parasites; that al¬ 
though macrophages can ingest vigorous 
parasites, they cannot digest them; or that 
macrophages are ineffectual in immunity 
because they are more active in acute per¬ 
nicious malaria than in cases of spontane¬ 
ous cure.. Many of the ideas, however, were 
incident upon the use of human material 
which precluded closely spaced observa¬ 
tions and rarely came to the necropsy table 
unless the defense mechanisms of the body 
were overwhelmed. 
Doubt of the functional significance of 
phagocytosis has been largely dispelled by 
the closely spaced serial observations of 
tissues during initial infections and super¬ 
infections first made by Cannon and Tali¬ 
aferro (1931) in birds and Taliaferro and 
Cannon (1936) in monkeys. The latter 
observations on Central American monkeys 
infected with P. brasilianum seem directly 
Endothel Adv 
Eryth Macrophage 
Mea Lymph 
Parasitised eryth Med Lympla 
Plate I 
Comparative phagocytic activity of the splenic macrophages in the Billroth cords at different stages 
in malaria. Central American monkeys infected with P. brasilianum. x 1200. Modified from Taliaferro 
and Cannon. 
Pig. 1. Sluggish phagocytosis during the natural immunity of the initial acute rise of the infection. 
The macrophages contain a small amount of parasitic and red cell debris. 
Pig. 2. Intense phagocytosis during the acquired immunity at the crisis which is associated with 
the termination of the initial acute rise. The macrophages are engorged with parasitized erythrocytes. 
Pig. 3. Pigment and comparatively indigestible debris remaining in the macrophages about two days 
after the crisis. These materials disappear within a few months. 
