PATHOGENIC BACTERIA. 149 



Colonies on gelatine plates in an atmosphere of hydrogen. 

 Small colonies. After four days a thick centre and radiating 

 wreath-like periphery, like the colonies of bacillus subtilis. 



High Stab-Culture. (The gelatine having 2 per cent, glucose 

 added and filling the tube.) Along the lower portion of the needle- 

 track, a thorny-like growth, little needle-like points shooting 

 out from a straight line. The whole tube becomes clouded as 

 the gelatine liquefies, and then the growth settles at the bottom 

 of the tube. 



Agar. At brood-heat, on agar, the growth is quite rapid, and 

 at the end of forty-eight hours gas bubbles have formed and the 

 growth nearly reached the surface. 



Bouillon. Adding glucose to the bouillon gives a medium in 

 which an abundant growth occurs. 



Cultivation from Spores. Kitasato, by exposing a portion of sus- 

 pected material to a temperature of 80 C. for one hour, killed off 

 all the spores save those of tetanus, which were then cultivated. 



Staining. All the ordinary stains, Gram's method also; the 

 spores being colored in the usual way. 



Pathogenesis. A small amount of the pure culture injected 

 under the skin of experiment animals will cause, in two to three 

 days, death from true tetanus, the tetanic condition starting 

 from the point of infection. At the autopsy nothing characteristic 

 or abnormal is found, and the bacilli have disappeared, except 

 near the point of entrance. This fact is explained as follows : 



Several toxic products have been obtained from the cultures, 

 and they are produced in the body, and give rise to the morbid 

 symptoms. These have been isolated, and when injected singly 

 cause some of the tetanic symptoms. The virus enters the 

 circulation, but does not remain in the tissues. The spores are 

 very resistant to heat, drying, and chemicals. 



Four toxins (among them tetanin, tetanotoxin. and spasmo- 

 toxin) have been found. The blood and the urine contain the 

 toxin and are fatal to animals. 



Immunity. Kitasato, by inoculation of sterilized cultures, has 

 caused immunity to the effects of virulent bacilli. 



An anti-toxin obtained by Tizzoni and Cattani from the serum 

 of animals made immune by sterilized cultures has been used 



