382 BACILLI WHICH CAUSE PUTREFACTION. 



liquefaction of the gelatine extends further ; in the peri- 

 phery of this area actively moving rods are found, and 

 also some which show distinct cilia, as well as convoluted 

 threads which are called spirilla and spirulina. Peculiar 

 zooglaea formations often extend from the circle of rays 

 in the form of clubs or screws, or of spirules twisted 

 like corkscrews. In 10 per cent, gelatine the migration 

 of the colonies is no longer observed. In meat infusion 

 there is active growth and the development of foul smell ; 

 on the other hand, in Nageli's and Cohn's nutrient solu- 

 tions there is only slight multiplication of the organisms. 

 Necessity for If the oxygen is expelled from the vessels employed for 

 cultivation and replaced by hydrogen, the growth takes 

 place only very slowly, and the liquefaction of the gelatine 

 is likewise very gradual, though ultimately complete. 

 The temperature optimum is between 20 and 24 C. 

 Spore formation is never observed ; nevertheless, drying 

 of the cultivations in a thin layer does not destroy the 

 Production of organisms. The bacilli set up putrefactive decomposition 

 putrefaction. j n fregb meat, and also in boiled and sterilised meat; 

 this, however, does not occur when the fluid added to 

 the meat has been filtered through plaster cylinders. 

 Experiments In animals small doses produce no pathogenic effect, 

 on animals. S0 mewhat larger doses often cause abscesses at the seat 

 of injection, large doses injected into the veins or sub- 

 cutaneously produce symptoms of poisoning in rabbits 

 and guinea-pigs. As the same effect was brought about by 

 cultivations which had been filtered through plaster of 

 Paris, it was evident that liquid poisonous materials 

 were the cause of the pathogenic action.* 



Proteus mirabilis (Hauser). 



Morphological These are rods *6 /*. in breadth and of very various 



characters. length ; they are sometimes almost round, sometimes in 



the form of rods 2 to 3'75 /*. in length. This form is 



distinguished from the preceding variety more especially 



by the much more frequent occurrence of involution 



* That this is not the whole truth is evident from Mr. Watson 

 Cheyne's paper on " Some Conditions of Infection," Brit. Med. Journal, 

 July, 1886. 



