28 A IDS TO BACTERIOLOGY 



Tidswell have shown that antivenomous serum is just 

 as specific as other antisera. 



Bacterial Mutability. The production of involution 

 forms (p. 3) and of attenuated bacteria (p. 14) have been 

 already dealt with. Appearance in different forms at 

 different times e.g., as a bacillus and leptothrix is called 

 Isomorphism. 



Bacteria that normally are ' acid-fast ' or ' Gram-posi- 

 tive ' may fail to resist decolorisation by acid in theZiehl- 

 Neelsen process, or may becoms ' Gram-negative,' when 

 old. This is most noticeable among the Streptothricice. 



Other changes in character occur especially in the colon- 

 typhoid group. Twort endowed a strain of typhoid bacilli 

 with lactose-fermenting power. Revis states that the 

 fermentation of a sugar or polyhydric alcohol takes place 

 in two stages a preliminary acid formation and a subse- 

 quent gas formation. Revis succeeded in causing an 

 organism to lose its power to produce gas while retaining 

 its capacity to produce acid, the resulting variety being 

 of a permanent character. 



It should be noted that an organism may ferment a 

 specific carbohydrate obtained from one dealer, and have 

 no action on the same substance as supplied by another. 



By exposure to ultra-violet rays Mine. Victor Henry 

 converted anthrax bacilli into cocci and other forms which 

 are apparently stable. It also appeared to lose its capacity 

 for secreting proteolytic enzymes. 



Simonini found thorium salts to modify morphology, 

 staining reactions, and physiological characters of Shiga- 

 Kruse and Flexner dysentery bacilli and B. diphtheria, 

 B. coli showing less response. 



Theile and Embleton showed that a guinea-pig pre- 

 viously sensitised to B. mycoides died after inoculation 

 with this organism, and the post-mortem appearances were 

 indistinguishable from those of anthrax. After passage 

 through the sensitised animal, the organism was capable 

 of producing disease in a normal animal. Similarly, 

 smegma and Timothy- grass bacilli produced in animals 

 specifically sensitised post-mortem appearances indis- 

 tinguishable from those due to an intraperitoneal injection 

 of tubercle bacilli. 



Dostal claims to have converted the tubercle bacillus 

 into a non-acid-fast and non-pathogenic organism. 



