316 



BACTERIA AND DISEASE 



The post-mortem signs are mainly three: The spleen -is greatly 

 enlarged and congested, is dark red in colour, friable to the touch, 

 and contains enormous numbers of bacilli ; ' the skin may show 

 exudations forming dark gelatinous tumours ; and the blood remains 

 fluid for some time after death, is black and tar-like, contains bubbles of 

 air, and shows other degenerative changes in the red corpuscles, whilst 

 the small Uood-vessels contain such vast quantities of bacilli that they 

 may be ruptured by them. Particularly is this true in the peripheral 

 arteries. Many of the organs of the body show marked congestion. 



The bacilli of anthrax are square-ended rods 1 yu broad and 

 4-5 IUL long. In the tissues of the body they follow the lines of the 

 capillaries, and are irregularly situated. In places they are so 

 densely packed as to form obstructions to the onward flow of blood. 

 In cultures they occur in chains end to end, having, as a rule, equal 



interbacillary spaces. But long filaments 

 and threads also occur. The exact shape 

 of the bacillus depends, however, upon 

 staining and spore formation. Both 

 these factors may very materially modify 

 the normal shape. The spores of anthrax 

 are oval endospores, produced only in 

 the presence of free oxygen, and at any 

 temperature between 18 and 41 C. On 

 account of requiring free oxygen, they 

 are formed only outside the body. The 

 homogeneous protoplasm of the bacillus 

 becomes granular ; the granules coalesce, 

 constituting spores. Each spore pos- 

 sesses a thick capsule, which enables it to resist many physical 

 conditions which kill the bacillus. When the spore is ripe, or 

 has exhausted the parent bacillus, it may either take on a resting 

 stage, or under favourable circumstances commence germination, 

 very much after the manner of a seed. The spores may infect 

 a farm for many months; indeed, cases are on record which 

 appear to prove that the disease on a farm in the autumn may, 

 by means of the spores, be carried on by the hay of the follow- 

 ing summer into a second winter. Thus, by means of the spores, 

 the infection of anthrax may cling to the land for very long periods, 

 even for years. Spores of anthrax can withstand 5 per cent, carbolic 

 acid or 1-1000 corrosive sublimate for more than an hour; even 

 boiling does not kill them at once, whilst the bacilli without their 

 spores are killed at 54 0. in ten minutes. When the spores are dry 

 they are much more resistant than when moist. The persistence of 

 the anthrax bacillus is due to its spores. 



The bacillus is aerobic, non-motile, and liquefying. Broth 



FIG. 28. Diagram of Bacillus of 

 Anthrax and Blood Corpuscles. 



