IMMUNOLOGY 851 



larial pigment (PI. 2, Figs. 3-5, which are from monkey 119; see also 

 Fig. 188) . The pigment is digested within a few months, as may be seen 

 by a study of animals in which relapses or superinfections do not inter- 

 vene. The various tissues gradually return to their normal histological 

 appearance, but as long as immunity lasts they retain their ability to 

 react more quickly than the tissues of nonimmune animals. 



These data raise the interesting immunological question as to whether 

 the death of the parasites before the crisis and that during or after the 

 crisis are due to the same factors. In other words, is acquired immunity 

 simply an enhancement of the high-grade natural immunity present from 

 the beginning, or is it due to an entirely new set of factors superimposed 

 on the natural condition? Certain facts tend to indicate that the two 

 mechanisms are essentially different. In the first place, during natural 

 immunity, all evidence indicates that phagocytosis is nonspecific, and 

 there is some evidence that only those parasites are phagocytosed which 

 are moribund or otherwise abnormal (Hartman, 1927; Gingrich, 1934; 

 Hegner and Hewitt, 1938; Hewitt, 1938). In the second place, Gingrich 

 found that the injection of large numbers of red cells breaks down 



CAPTION FOR PLATE ON FACING PAGE 



Plate 2. Intense phagocytosis of Vldunodium brasilianujn by macrophages in Central 

 American monkeys at the height of the crisis of the malarial infection (Figs. 1 and 2) 

 and malarial pigment, the residue of parasites after the intense phagocytosis, in the 

 macrophages shortly thereafter (Figs. 3-5). X 1450. (From W. H. Taliaferro and P. R. 

 Cannon, "Cellular Reactions during Primary Infections and Superinfections of Plasmodium 

 Brasilianum and Panamanian Monkeys," Journal of Infectious Diseases, LIX [July- 

 August, 1936], 72-125.) 



Figure 1. A Kupffer cell in the liver containing many recognizable parasitized and 

 unparasitized red cells, and a monocyte (Mon.) containing malarial pigment. Crisis of 

 infection. 



Figure 2. Two macrophages in the Billroth cord of the spleen containing many recog- 

 nizable parasitized and unparasitized red cells. Crisis of infection. 



Figure 3. A Kupffer cell in the liver containing malarial pigment. Two days after the 

 crisis. 



Figure 4. Two macrophages in the bone marrow containing malarial pigment. Two 

 days after the crisis. 



Figure 5. Four macrophages in the Billroth cord of the spleen containing malarial 

 pigment. Two days after the crisis. Figures 3, 4 and 5 were all taken from monkey 119 

 (see text Figure 188). Note that the Kupffer cell of the liver contains intermediate 

 amounts of malarial pigment between that found in the macrophages of the spleen and 

 of the bone marrow. 



