520 The American Naturalist. [June, 
finally came to the conclusion that the invested plants were 
destroyed by a true process of intracellular digestion. 
Sutton has recently given some valuable information in regard 
to tuberculosis in birds, which he says is more prevalent than in 
man. He tells us that the bacilli, from whatever place they may 
have come, get into the alimentary canal, and there penetrate into 
its walls. In some cases they may be taken up in the blood 
vessels, and getting into the general circulation, may finally be 
deposited in distant tissues of the body, such as the liver, lungs, 
or brain, and, in multiplying, cause the death of the animal. In 
the bowels, they are undoubtedly attacked by the leucocytes, and 
are surrounded, killed, and destroyed. Sometimes the battle may 
go against the defending force, when the bacilli are gaining an 
entrance, and then great numbers gather to reinforce their 
comrades. Many are killed, forming pus-cells, and others fuse 
together, as Metschnikoff saw them doing about the spores in 
Daphnia, and forming the giant cells. “These giant cells,” says 
Sutton, “are powerful antagonists, for’ I have seen one contain as 
many as fifty bacilli.” 
The relation of leucocytes to inflammation and fever is pretty 
generally admitted. It is easily demonstrated that, under certain 
stimulation, such as the exposure of a bit of the mesentery of an 
animal, or the introduction of some foreign body, the leucocytes 
appear on the spot, coming in blood vessels from distant parts ; 
and that they, in some way, penetrate the vessel walls, and appear 
in the tissue outside, ready to engage an enemy which may be 
present. As the last author referred to says: “ Zoologically 
considered, inflammation is, in essence, a local struggle between 
irritants and the white cells of the blood. When the whole of 
the blood is engaged in the struggle, as in ague, anthrax, and the 
like, we have general inflammation or fever. The different 
varieties of fever, when due to microorganisms, depend on the 
habits of specific bacteria; some are more virulent, others are 
slower in attaining maturity, or are more irritating to the tissues.” 
There is something wonderfully attractive in this theory of 
Metschnikoff’s, and of course when it became known, a great 
number of investigators at once began to make all kinds of 
