150 BACTERIA IN RELATION TO DISEASE 



organism (probably spores, for the most part) is taken up. The spores pass 

 uninjured through the stomach, and germinate in the intestine, setting 

 up intestinal anthrax, which mostly leads to general infection and death. It 

 is not known whether the bacteria have themselves the power of boring 

 through the uninjured mucous membrane of the gut, or whether a previous 

 laceration is necessary, such as might be caused by jagged splinters of food. 

 In small animals, such as mice, which succumb very quickly (1-3 days), 

 the disease causes no conspicuous change in the organs, but in sheep and cattle 

 its effects are more conspicuous. Spores, being formed only where there is 

 free access of oxygen, never occur in the diseased tissues or the dead body. 

 They arise under suitable conditions of temperature (i8-3O C.) in the 

 bloody dejecta of sick animals, and also in carcases that arc not buried 

 deeply underground. 



3. TETANUS (132) (Fig. 28, e). Lock-jaw or tetanus is caused by a 

 metatrophic bacterium very widely distributed in the soil, where it probably 

 gives rise to various putrefactive and fermentative processes. The nature of 

 these processes is in all probability dependent upon the food that happens to 

 be available, for the tetanus organism is able both to split up sugar, and in 

 albuminous substances free from sugar to decompose protcids into CO 2 , SH 2 , 

 CH 4 , mercaptan, and free hydrogen. The pathogenic properties of the 

 organism are due, not to any of these substances, but to a violent poison 

 which has not yet been isolated in a perfectly pure form. Tetanus is 

 a typical traumatic infection that arises only by the contamination of 

 wounds by matter containing the bacillus earth or the dust of hay or 

 straw, for example. The bacilli grow only in the wound itself, and even 

 here but sparingly. They never spread to other parts of the body. 



Bacillus (Plectridium) tetani is a slender motile rod 2.4^1 long by 0-3 

 0-5 M thick. It is inclined to filamentous growth, particularly in anaerobic 

 cultures. In aerobic cultures the moss-like colonies grow only in the deeper 

 layers of the gelatine. Before sporulation, which is very constant, the rods 

 swell up at one end, and in this dilated part the spore appears. The drum- 

 stick shape, together with the peritrichous type of ciliation, places the 

 organism in the genus Plectridium. 



Two other bacteria of the soil with saprogenic and zymogenic proper- 

 ties (B. Chauvei and B. oedematis maligni) give rise to quarter-evil and 

 malignant oedema respectively. 



4. DIPHTHERIA (Bacillus diphtheriae, Loeffler; Corynebacterium 

 diphtJieriac, Lehmann and Neumann [133]; Figs. 28, f and 14, /i). This 

 bacterium is found almost without exception in the outer layers of the diph- 

 theritic false membrane. In consequence of this tendency to superficial 

 growth, it seldom spreads to other parts of the body, but remains confined 

 to those cavities which are the usual seat of the disease. Exceptions to this 

 do, however, sometimes occur. It is often found in the throat in association 



