144 Chapter VI 



exudation, It is the macrophages which specially manifest phago- 

 cytosis and they are often found crammed with the injected bacteria, 

 as I was able to assure myself after injections of typhoid cocco-bacilli. 

 The natural immunity of alligators (Alligator mississipiensis) persists 

 not only at the temperature of the incubator (37 C.), but also at room 

 temperature (20 22 C.). 



Passing in review the animal kingdom we must pause for a 

 moment to consider the natural immunity of birds or lower warm- 

 blooded Vertebrates. The classic example of this immunity is that 

 of the fowl against anthrax. It has long been known that birds resist 

 [153] inoculation with anthrax or only exhibit a feeble receptivity; though 

 smaller birds are for the most part susceptible to anthrax, the pigeon 

 is much less so and the fowl presents a case of the most pronounced 

 immunity. It was believed to be absolutely refractory until the 

 experiments of Pasteur and Joubert 1 , who found a sure method of 

 suppressing this immunity. Fowls that had been inoculated with 

 the bacillus were immersed up to the thighs in cold water in order to 

 bring down their temperature. It was found that, under these con- 

 ditions, the anthrax bacillus developed at the seat of inoculation and 

 later became generalised in the blood, and invariably caused death. 

 It was concluded from this that the natural immunity of the fowl 

 was dependent on its very high normal temperature (41 42) which 

 interfered with the pathogenic functions of the anthrax bacillus. 



Hess 2 studied the mechanism of this immunity of the fowl and 

 pointed out the important part that phagocytosis plays in the de- 

 struction of the inoculated bacteria. 



These researches were resumed in my laboratory by Wagner 3 . 

 Having established that the anthrax bacillus develops readily in the 

 blood and the blood serum of fowls, outside the organism, at high 

 temperatures (42 43 C.), he came to the conclusion that the 

 lowering of the temperature of the body of the fowls by immersing 

 them in water produced, not a reinforcement of the bacillus, but 

 a weakening of the resisting power of the animal. He was able 

 to convince himself that this resistance exhibits itself in the activity 

 of the phagocytes which ingest and destroy the anthrax bacillus in 

 its vegetative state. In the normal fowl the phagocytosis is rapid 

 and very pronounced, whilst in a fowl that has been refrigerated this 



1 Bull Acad. de med., Paris, 1878, p. 440. 



2 Virchow's Archiv, Berlin, 1887, Bd. cix, S. 365. 



3 Ann. de VInst. Pasteur, Paris, 1890, t. iv, p. 570. 



