638 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



speculation, then exposing half an hour to a temperature of 80 to kill 

 all vegetative forms and subsequently making subcultures. If other 

 spore-bearing bacteria are present considerable difficulty may be encount- 

 ered. Subcutaneous inoculations of mice or guinea pigs is a good method 

 for demonstrating the presence of the organism, but pure cultures should 

 be combined with some aerobe (say B. coll) to secure results. 



The B. tetani is about 2/1 to $fj. in length by .3/x to .8/1 in width with rounded ends. 

 The vegetative rods are uniformly cylindrical but the terminal spores give a "drum 

 stick " appearance (Fig. 1 1 1). The arrangement is usually single, but threads may occur 

 especially in old cultures. The organism forms round terminal spores which have a 



FIG. in. Tetanus bacilli showing end spores. (After Kolle and Wassermann from 



Stitt.) 



diameter of i/x to 1.5/1. The young bacilli are motile and possess 50 to 70 peri tri chic 

 flagella. Motility is lost with sporulation. The bacillus is stained by the aniline dyes 

 and is Gram-positive. The spores are readily demonstrated by the special stains. The 

 range of temperature for growth is from about 14 1045 with an optimum about 37. 

 The organism is usually considered an obligate anaerobe though experimentally 

 aerobic strains have been developed but with loss of pathogenic and toxogenic properties. 

 Pure cultures do not develop in an atmosphere of carbon dioxide. Media for the 

 cultivation of the bacillus should be slightly alkaline and should contain for best 

 growth about 2 per cent of glucose or i . 5 per cent sodium formate. The addition of 

 pieces of fresh raw sterile tissue is valuable. On agar at 37 colonies appear in forty- 

 eight hours which show microscopically, a mass of tangled threads resembling colonies 

 of B, subtilis or Bact. anthracis. In broth a cloudiness is produced in twenty-four to 

 thirty-six hours with the development of gas and a very disagreeable odor. In gelatin 

 the colonies develop more slowly than on agar and show liquefaction. In old stab 



