308 ANTHRAX 



The lymphatic system generally is much affected. The 

 glands, especially the mediastinal, mesenteric, and cervical 

 glands, are enlarged and surrounded by oedematous tissue, the 

 lymphatic vessels are swollen, and both glands and vessels may 

 contain numberless bacilli. The heart may be in a state of cloudy 

 swelling, and the blood in its cavities contains bacilli, though in 

 smaller numbers than that in the capillaries. The intestines are 

 enormously congested, the epithelium more or less desquamated, 

 and the lumen filled with a bloody fluid. From all the organs 

 the bacilli can be easily isolated by stroke cultures on agar. 



It is important to note the existence of great differences in 

 susceptibility to anthrax in different species of animals. Thus 

 the ox, sheep (except those of Algeria, which only succumb to 

 enormous doses of the bacilli), guinea-pig, and mouse are all very 

 susceptible, the rabbit slightly less so. The last three are of 

 course most used for experimental inoculation. We have no 

 data to determine whether the disease occurs among these in the 

 wild state. Less susceptible than this group are the horse, deer, 

 goat, in which the disease occurs from time to time' in nature. 

 Anthrax also occurs epidemically in the pig, often from the 

 ingestion of the organs of other animals dead of the disease. It 

 is, however, doubtful if all cases of disease in the pig described 

 on clinical grounds as anthrax are really such, and a careful 

 bacteriological examination is always advisable. The human 

 subject may be said to occupy a medium position between the 

 highly susceptible and the relatively immune animals. The 

 white rat is highly immune to the disease, while the brown rat 

 is susceptible. Adult carnivora are also very immune, and the 

 birds and amphibia are in the same position. 



With these differences in susceptibility there are also great 

 variations in the pathological effects produced in the natural or 

 artificial disease. This is especially the case when we consider 

 the distribution of the bacilli in the bodies of the less susceptible 

 animals. Instead of the widespread occurrence described above, 

 they may be confined to the point where they first gained access 

 to the body and the lymphatic system in relation to it, or may 

 be only very sparsely scattered in organs such as the spleen 

 (which is often not enlarged), the lungs, or kidneys. Neverthe- 

 less the cellular structure of the organs even in such a case may 

 show changes, a fact which is important when we consider the 

 essential pathology of the disease. 



Experimental Inoculation. Of the animals commonly used 

 in laboratory work, white mice and guinea-pigs are the most 

 susceptible to anthrax, and are generally used for test inocula- 



