242 ANTHRAX BACILLUS 



sufficiently coagulate after death. Postmortem rigidity is not strong 

 nor does it continue very long, and putrefactive changes with gas 

 formation rapidly set in. Blood oozes from the mouth, the nose, 

 and the anus. The mucous and serous membranes are enormously 

 congested and show petechice and ecchymoses. Hemorrhages in the 

 connective tissue are also found in various places. The subcutaneous 

 and intramuscular connective tissues show an cedematous, gelatinous 

 infiltration with hemorrhagic patches here and there. The lymph 

 glands are swollen and edematous. The spleen is generally much 

 swollen, much congested, its pulp very soft, and the capsule tense. 

 It ruptures easily, and an almost fluid pulp mass may be discharged 

 spontaneously. The liver and kidneys are swollen, congested, and, 

 when cut into, discharge much dark blood and present a dull surface 

 indicating parenchymatous degeneration. The lungs and the brain 

 are likewise hyperemic and edematous. The mucosa of the intestines 

 is swollen, dark, sometimes necrotic, often raised in patches by 

 edematous and hemorrhagic infiltration in the form of ridges or 

 globular masses. The blood, when examined microscopically, shows 

 a very marked increase in the number of leukocytes (leukocytosis or 

 hyperleukocytosis) and enormous numbers of anthrax bacilli. These, 

 however, are found in the capillaries of the internal organs rather 

 than in the larger vessels. Sometimes in very rapid so-called ful- 

 minant cases the anatomical changes are not as well marked as 

 described above, because the fatal intoxication has been so rapid that 

 the characteristic anatomical changes have not had sufficient time to 

 develop. The spleen, however, is generally very congested, enlarged 

 and softened in all cases. 



The Discovery of the Bacillus. Anthrax bacilli were first seen in 

 the blood of animals dead from the disease by Pollender and Brauell. 

 The latter also made some successful inoculation experiments on 

 animals. These were later repeated and extended by Davaine, who 

 had previously written concerning the rod-shaped bodies in the blood 

 of animals which had died from splenic fever. The etiology of anthrax 

 was first firmly established by pure culture and animal experiments 

 by Robert Koch, in 1876, who was also the first to discover the spores 

 of the bacillus. 



Morphology. The Bacillus anthracis is a rod-shaped bacterium 

 1.5 to 10 micra long (average length, 4 micra), and 1 to 1.25 micra 

 thick. It is, therefore, one of the largest pathogenic bacteria. It is not 

 motile. The exact morphology of the bacilli can best be studied in 

 the blood of animals which have just died or are in the agonal stage 

 of the disease. The bacilli appear in large numbers in the blood ten to 

 twelve hours before death. Examination of the unstained blood of a 

 mouse or guinea-pig in a moist cover-glass preparation shows trans- 

 parent, colorless, cylindrical rods which have no motility whatever 

 between the erythrocytes. Individual bacilli or short chains of two, 

 three, or four bacilli occur. Long chains or spores are never seen in 



