130 CHEMISTRY OF THE ANIMAL PARASITES 



positive results with immune serum from rabbits; they found no poison- 

 ous agent in trypanosome substance. ^^ The fact that trypanosomes 

 themselves readily become immune to various trypanocidal chemicals 

 has been demonstrated and extensively studied in Ehrhch's laboratory. 

 Gonder^o j^^s made the interesting observation that trypanosomes 

 which can be stained by certain vital stains, become unstainable while 

 alive if immune to arsenic compounds, suggesting that this immunity 

 is associated with considerable structural or chemical changes. 



Plasmodium malariae undoubtedly produces toxic substances, 

 which seem to be of such a nature that they do not diffuse from the red 

 corpuscle, but are only liberated when the corpuscle breaks up on 

 the maturation of the parasite. In this way the characteristic par- 

 oxj^smal manifestations of the disease are produced. The nature of 

 the poison or poisons is unknown, but we have evidence that it is 

 hemolytic, since malarial serum may hemolyze normal corpuscles, ^^ 

 and extracts of the parasites are stronglj^ hemolytic (Brem-^); prob- 

 ably the malarial hemoglobinuria is caused by this hemolj-sis. Pre- 

 sumably malarial poisons are not extremely toxic for parenchymatous 

 cells, since the parenchymatous lesions in malaria seem to be relatively 

 slight as compared with the intensity and duration of the intoxication. 

 Some authors state that the toxicity of the urine is increased after 

 the paroxysm,-^ which, however, does not necessarily indicate that 

 a poison formed by the parasites is excreted in the urine. Immunity 

 seems to be seldom developed against the malarial poison or against 

 the parasite itself, although some persons seem to be naturally im- 

 mune, w^hile some acquire immunity through previous infection.-^ 

 The blood of persons with malaria seems to contain no antibodies for 

 the parasite (Ferrannini),^^ although it seems to have some antihemo- 

 lytic power (Brem). (Concerning the pigment present in the ma- 

 larial parasites see "Pigmentation," (Chap, xviii). 



Sarcosporidia of sheep yield aqueous and glycerol extracts that 

 are highly toxic for rabbits (Pfeiffer), the poisonous constituent of 

 which was called sarcocystin by Laveran and Mesnil.-^ This is so 

 highly toxic that 0.0001 gm. is fatal to rabbits (per kilo), other ani- 

 mals being less susceptible. It loses its toxicitj'' on heating at 85° 

 for twenty minutes, and is impaired at 55-57° for two hours. It 



1" Hintze (Zeit. f. Hyp;., 1915 (80), 377) obtained little immunity with T. 

 brucei, hut Scliiiling and Kondoni (Zeit. Imiminitat., 1913 (IS). t)51) obtained'a 

 poison from Nagana trypanosomes which produced active imnumity in mice. 

 When trypanosomes are killed by weak electric currents they may liberate an 

 active poison (Uhlenhutli and Seyderhelni, Zeit. Immimitjit., 1914 (21), 366). 



"Zeit. Immunitilt., 1913 (15), 257. 



" See Regnault, Kevue de MM., 1903 (23), 729. 



"Arch. Int. Med., 1912 (9). 129. 



"(Quoted from HIanchurd, Arch. d. Parasitol., 1905 (10), 83; this article gives 

 a r6sum(' of tlie siibj(!c( of the iox'w. substances produced by the animal parasites. 



" See Celli, Cent. f. Hakt., 1900 (27), 107. 



" Kiforma Med., 1911 (27), 177. 



=» Compt. Rend. Soc. Bio!., 1899 (51), 311. 



