36 BACTERIA. 



70 C., whilst certain forms of "Light " bacilli can, accord- 

 ing to Fischer, grow luxuriantly at a temperature of o C. 



It should be remembered, however, that arthrospores 

 are much less resistant to all germicidal reagents than 

 are endospores j indeed, they are able to withstand a 

 temperature only about as high as that at which the 

 vegetative forms succumb ; whilst some of the endospores 

 are capable of withstanding dry heat of 105, 110, and even 

 130 C. They are certainly more resistant to the action of 

 some of the weaker germicidal reagents, but they withstand 

 for a short time only, or not at all, the action of the more 

 powerful ones. 



From the nature of the dense membrane that surrounds 

 these spores, their staining has always been a matter of 

 extreme difficulty. They stood out most distinctly as clear 

 spaces in the deeply stained protoplasm of the cell, but could 

 not be stained. By subjecting the spore-containing organisms 

 to the action of dry heat at 110 C. for half an hour or an 

 hour, as suggested by Buchner, or by exposing them to the 

 action of concentrated sulphuric acid for fifteen seconds, or 

 to a longer treatment with concentrated caustic potash, the 

 membrane is so altered that the staining reagents are enabled 

 to penetrate into the substance of the spore and act on its 

 protoplasm, and impart to it a characteristic colour. If this 

 heating be excessive the protoplasm of the bacillus may be 

 destroyed when it in turn refuses to take on the stain, 

 although the spore itself may, under these circumstances, be 

 stained most beautifully, this fact also indicating that the 

 spore is more resistant to the action of heat than is the 

 vegetative cell. Hueppe, Babes, and Neisser have all 

 described arthrospores as making their appearance at the 

 end of Koch's cholera bacillus, which may become free, says 

 Hueppe, and from which, he thinks, he has seen the bacillus 

 being developed. 1 



1 In order to stain endospores, the best fluid to use is probably Ehrlich's 

 aniline water fuchsin solution. Sections are left in this for several clays, 

 they are then decolorised with 25% solution of nitric acid, washed thoroughly 

 in water and alcohol, to which a trace of ammonia has been added ; a con- 

 trast stain is obtained by treating for a few minutes with a dilute solution 

 of methylene blue. In some cases the acid removes the fuchsin from 

 the spores also ; it is then well to wash simply with alchohol and stain 

 with methylene blue as a contrast stain. Instead of leaving cover glass 

 preparations for so long a period in the fuchsin they may be heated along 



