TETANUS. 233 



cesses arranged radially at the brighter margin. The gelatin is 

 slowly liquefied. 



In high gelatin stab-cultures growth confined to the lower por- 

 tion of the line of inoculation appears after about a week. 

 From the grayish-white bacterial mass innumerable small, pointed 

 processes extend in every direction into the gelatin, giving the 

 culture a characteristic appearance suggestive of a large-branched 

 fir-tree. In the second week liquefaction sets in and obliterates 

 this appearance. The process advances slowly, until gradu- 

 ally the entire culture is converted into a turbid, grayish-white, 

 viscid mass, of which the upper portion subsequently becomes 

 clear, while the bacilli sink to the bottom as a cloudy gray mass. 



On agar-plates delicate colonies develop, which with low 

 powers of the microscope appear to consist of a network of fine 

 threads such as is not usually seen in anaerobic cultures. 



On agar stab- cultures the growth is similar to that upon gela- 

 tin, although not so pronounced. It takes place much more 

 rapidly at the temperature of the body. Stab-cultures in a high 

 layer of grape-sugar agar develop within from twenty-four to 

 forty-eight hours close to the surface. They exhibit the character- 

 istic odor, and are usually attended with abundant gas-formation. 



In glucose-bouillon growth at 37 C. (98.6 F.) is very ener- 

 getic. On account of the abundant formation of gas it is well 

 not to close the bouillon-flasks too tightly. The bouillon is at 

 first rendered quite turbid ; after standing for weeks the bac- 

 terial masses settle to the bottom as a grayish-white layer, so 

 that on careful suction of the overlying clear fluid a solution of 

 toxin free from bacteria is obtained. This may be secured with 

 greater certainty by filtering the bouillon-cultures through porce- 

 lain cylinders. 



The tetanus-bacillus develops in milk without causing any 

 change. 



Upon potatoes a moist invisible deposit forms similar to that 

 caused by typhoid-bacilli (Vaillard and Vincent). 



Tetanus in Animals. Tetanus occurs under natural 

 conditions in horses, sheep, and neat cattle ; it has not been 

 observed in dogs, and especially not in fowl. The mouse is 

 the animal best adapted for the experimental development 

 of tetanus. Of an old bouillon-culture (freed of bacilli by 

 filtration, or by careful decanting) o.ooi cu. cm., and 

 frequently still much smaller amounts, suffice on subcu- 

 taneous injection to cause death in white mice (from twelve 

 to fifteen grams in weight) within twenty-four hours. The 

 guinea-pig is almost equally susceptible. The rabbit is 

 much less susceptible : not less than from o. 5 to I cu. cm. 



