Pathogenesis 



615 



Gelatin Punctures. In gelatin puncture cultures the 

 growth is quite characteristic, and 

 the tendency of the bacilli to grow 

 anaerobically is well shown (Fig. 

 1 8 1 ) . The development takes place 

 all along the line of puncture, but is 

 more marked below than at the sur- 

 face. The growth occurs in a pecu- 

 liar form, resembling superimposed 

 disks, each disk separate from its 

 neighbors and consisting of an area 

 of clouded grayish gelatin reaching 

 almost to the walls of the tube. 

 This growth develops slowly, and 

 causes a softening rather than an 

 actual liquefaction of the gelatin. 



Agar-agar. Upon agar-agar and 

 blood -serum a very delicate, trans- 

 parent grayish line develops along 

 the path of the needle. It does not 

 grow upon potato. 



Vital Resistance. The bacilli 

 grow well at the room tempera- 

 ture, but much better at the tem- 

 perature of the incubator (37 C.). 



Pathogenesis. The organisms 

 are pathogenic for a variety of ani- 

 mals, notably hogs, rabbits, mice, 

 white rats, pigeons, and sparrows. 

 The guinea-pig, which is usually the 

 victim of laboratory experiments, 

 is immune. Field- and wood-mice, 

 cattle, horses, asses, dogs, cats, 

 chickens, and geese are also im- 

 mune. 



When mice are inoculated, they 

 soon become ill, lose their appetites, 

 mope in a corner, and are not 

 readily disturbed. As the disease 

 becomes worse they assume a sit- 

 ting posture with the back much 

 bent and the eyelids glued together 

 by adhesive pus. When death comes, in the course of forty 



Fig. 181. Bacillus mu- 

 risepticus (mouse-septice- 

 mia), gelatin stab culture, 

 twelve days old (Curtis). 



