TEXT-BOOK OF BACTERIOLOGY. 219 



ately under the serous covering. Here we may see them isolated 

 or joined in long threads, but scarcely ever does a cell venture 

 deeper down into the tissue. 



It is true that these appearances can only be observed distinctly 

 when the animal is examined as soon as possible after death. The 

 longer the time that elapses, the more the picture alters. The 

 bacilli which, as long as life lasted, confined themselves to the sur- 

 face of the organs, and scarcely ventured to take a few timid steps 

 toward the interior of them, possess the faculty of thriving in the 

 dead body, in which they multiply immensely. " It is evident," 

 says Gatlky, "that, aided by their motile power and by the 

 serous saturation of the muscles of the abdomen and breast, they 

 pass from the subcutaneous oedema, their proper home, into the 

 thoracic and abdominal cavities and thence from the surface into 

 the interior of the organs." And there they are found in great 

 quantities. First they fill the entrances with a close network; they 

 then advance further into the deeper parts (forming long threads 

 in the lungs) ; they grow into vessels, and at length fill the tissues 

 as completely and in as large masses as do t]\e anthrax bacilli. 



In mice this state of things will always and from the first be 

 found, though not in Guinea-pigs and rabbits. With mice' the 

 space for action is so small that the differences just described have 

 not room to develop. The bacilli penetrate during life into the in- 

 terior of the mouse's diminutive organs, fill out the tissues, burst 

 the walls of the vessels, and are thus carried in the blood to the 

 most distant parts. 



Moreover, since the serous effusion in the subcutaneous cellular 

 tissue of a mouse is very small, while the spleen is almost always 

 greatly enlarged, dark-colored, and generally softened, it will 

 readily be comprehended that malignant oedema may easily be 

 confounded with anthrax in such cases, and that only careful ex- 

 amination can detect the error. 



It was with the oedema bacilli that Roux and Chamberland 

 most conclusively proved the important part which the excretions, 

 the "substances solubles," play in causing immunity. If they kept 

 bouillon cultures for ten minutes at a heat of 115° C, or if thej^ fil- 

 tered them through porcelain tubes, about 100 c.cm. of the liquid 

 without anj' bacteria sufficed, when injected in three several doses 

 into the abdominal cavity of Guinea-pigs, to render them proof 

 against inoculation with the bacteria themselves. The success was 

 still greater when, instead of the cultures, the blood-serum obtained 

 from dead victims was filtered. An injection of about one cubic 

 centimetre, repeated seven or eight times on as many consecutive 

 days, produced the desired effect. 



