PROTOZOA 135 



tiou iu tlie number of eosinophile leucocytes, Avhicli also show evi- 

 dences of disintegration in the bone-marrow and lymph-glands. Such 

 large injections are fatal, which suggests that the eosinophilia has a 

 protective influence. In favor of this view is the observation of 

 Milian,*^ who found that sarcosporidia in beef are destroyed by a 

 violent leucocytic reaction, the prevailing cell being the eosinophile. 

 As the eosinophile increase does not occur until several days after 

 the infected flesh is eaten, the chemotactic substance is not liberated 

 from the encapsulated trichinella? when tlieir capsules are digested 

 ofit" in the gastric juice, but comes either from the free larvae, or from 

 the degenerated muscles in which they burrow. Coincident bacterial 

 infection may reduce the number of eosinophiles. Herrick " finds 

 that extracts of Ascaris himhricoides cause a notable eosinophilia, but 

 only when the animal has been sensitized previously with the same 

 extract, the active agent of which is a protein ; this suggests a rela- 

 tionship between parasitic and anaphylactic eosinophilia.'^^ That the 

 eosin()j)hiles play a part in the immunity reactions obsei"\'ed in the 

 hosts of animal parasites is indicated by the fact that hydatid fluid 

 loses its antigenic properties when in contact with eosinophiles.'*^ 



PROTOZOA 



These unicellular forms possess all the chemical characters of the 

 (^ells of higher forms, even to the more specialized constituents. Thus 

 it has been demonstrated that protozoa contain proteolj^tic enzymes,^ 

 and that they secrete an acid into their digestive vacuoles.^ On the 

 other hand, Amcfha coll does not seem to digest the red corpuscles and 

 the bacteria that it takes up.^° Whether the Anmha coli produces 

 any toxic materials, specific or non-specific, has not yet been deter- 

 mined, but the necrosis that it produces in liver abscesses, when bac- 

 terial cooperation can often be excluded by culture, strongly indi- 

 cates the production of necrogenic substances. Apparently these sub- 

 stances are not chemotactic, in view of the absence of leucocytic ac- 

 cumulation which is characteristic of the lesions of amebic dj^sentery. 

 There is also no evidence, clinical or experimental, that amebic in- 

 fection causes the formation of anti-substances of any kind in the 

 body of the host. The spontaneous recovery from amebic and other 

 protozoan infections, however, may be considered as indicating the 

 development of an immunity against these organisms.^^ Numerous 



6 Bull, et Mem. Soc. Anat.. 1901 (Ser. G, T. 3i, 32.3. 



7 Arch. Int. Med., 1913 (11), 165. 



Ta Supported liv Paulian, Tresse IMed.. 191.1 (23), 403. 



■b Weinberg' and Sepuin. Ann. Inst. Pasteur. 1916 (30), 323. 



sMouton. Conipt. Rend. Soc. Biol., 1901 (.13), 801. 



9 Le Dantec, Ann. Inst. Pasteur, 1890 (4), 776; Greenwood and Saunders, .Tour, 

 of Phvsiol., 1894 (16), 441. 



Jo^fusgrave and Clegg, Bureau of Gov't. Laboratories, ^lanila, 1904, Xo. 18, 

 p. 38. 



11 Concerninfr immunitv to protozoan infections see Schilling-, Kolle and Wasser- 

 mann's Handbuch, 1913 '(7), 566. 



