THE BACILLUS AND THE BACTERIOLOGY OF TETANUS 223 



Growth in Media. The bacillus of tetanus grows in ordinary nutrient 

 gelatin and agar of a slightly alkaline reaction. The addition to the 

 media of 1.5 per cent, of glucose causes the development to be more 

 rapid and abundant. It also grows abundantly in alkaline bouillon 

 under an atmosphere of hydrogen. On gelatin plates the colonies 

 develop slowly; they resemble somewhat the colonies of the bacillus 

 xitlitiliff, and have a dense, opaque centre surrounded by fine, diverg- 

 ing rays. Liquefaction takes place more slowly, however, than with 

 the bacillus subtilis, and the resemblance to these colonies is soon 

 lost. 



The colonies on agar are quite characteristic. To the naked eye 

 they present the appearance of light, fleecy clouds; under the micro- 

 scope, a tangle of fine threads. 



The stab cultures in gelatin exhibit the appearance of a cloudy, linear 

 mass, with prolongations radiating into the gelatin from all sides. 

 Liquefaction takes place slowly, generally with the production of gas. 

 In stab cultures in agar a growth occurs not unlike in structure that of 



FIG. 84 



4 



' 



Tetanus bacilli with spores in distended ends. X 1100 diameters. 



a miniature pine-tree. Alkaline bouillon is rendered somewhat turbid 

 by the growth of the tetanus bacillus. In all cases a production of gas 

 results, accompanied by a characteristic and very disagreeable odor. 

 It develops in milk without coagulating it. 



Resistance of Spores to Deleterious Influences. The spores of the 

 tetanus bacillus are very resistant to outside influences; in a desic- 

 cated condition they retain their vitality for years, and are not destroyed 

 in two and a half months when present in putrefying material. They 

 withstand an exposure of one hour to 80 C., but are killed by an ex- 

 posure of five minutes at 100 C. to live steam. They resist the action 

 of 5 per cent, carbolic acid for ten hours. A 5 per cent, solution of 

 carbolic acid, however, to which 0.5 per cent, of hydrochloric acid has 

 been added, destroys them in two hours. They are killed when acted 

 upon for three hours by bichloride of mercury (1: 1000), and in thirty 

 minutes when 0.5 per cent. HC1 is added to the solution. Silver nitrate 

 solutions destroy the spores in one minute in 1 per cent, solution and 

 in about five minutes in 1 : 1000 solution. 



