TETANUS. 289 



forming a kind of cloud ; the gelatine becomes softened, 

 and there is emitted a peculiar fusty smell which appears to 

 be almost characteristic of this organism. 



Most of the earlier experiments were somewhat unsatis- 

 factory, and considerable doubt was cast on this organism as 

 a producer of tetanus from the fact that in many cases pus that 

 was known to contain this specific bacillus, and even old pure 

 cultivations of the organism, failed to set up the characteristic 

 symptoms when inoculated in the usual manner. More 

 recent observers, however, have pointed out that the tetanus 

 bacillus, like many others of the septicaemia group, is virulent 

 only so long as it is grown under anaerobic conditions. This 

 is especially the case in those organisms in which there has 

 not been time for the spores to develop ; so that when 

 grown in the presence of free oxygen (when that is possible), 

 or when exposed to the air after the growth has been com- 

 menced under favourable conditions, and has gone on for 

 some time, but before there has been time for the formation 

 of spores, the organism rapidly loses its virulence, or, as we 

 have seen, dies off altogether. Experiments made by inocu- 

 lating the pus from tetanic patients often gave entirely nega- 

 tive results. Here it was evident that the failure was due, 

 in many cases at any rate, to the fact that the pus with its 

 contained organisms had been exposed to the air for some 

 time, and the bacilli had been compelled to grow under 

 conditions unfavourable to the retention of their specific viru- 

 lence, before they were used for purposes of inoculation. In 

 such organisms, as we should expect, it is found that spores 

 are not seen, or they are very imperfectly developed, and it 

 may be in the case of the older cultures, where these 

 spores are developed into the young bacilli, that these, 

 not having attained their full resisting power, die off very 

 readily in the presence of oxygen. By paying attention to 

 this point it has gradually been proved, almost beyond doubt, 

 that the tetanus that may be produced in white mice or 

 guinea-pigs by the inoculation of small particles of garden 

 earth, is of the same nature as the tetanus that is produced 

 by the inoculation of the pus from a primary wound which 

 has apparently given rise to tetanus in the human subject. 

 Further, now that the conditions under which the organism 

 exists have been studied, and its anaerobic character 

 recognized, pure cultivations have been made, and it has 



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