ETIOLOGY 173 



opalescent liquid becomes quite thick and dark-colored but not viscid. 

 When the opalesence appears the milk is strongly alkaline. The pro- 

 cess seems to be a form of saponification of the fat globules due to the 

 presence of the alkali produced by the bacteria. 



Indol. — In Dunham's solution the growth is quite feeble. Ordi- 

 narily no indol reaction is obtained although it has been observed in 

 a few cultures obtained from different epizootics. 



Gas production. — In peptonized bouillon containing i per cent, 

 dextrose, gas appears within 24 hours and continues to form for from 

 three to five days. During the first day from one-fourth to one-half of 

 the total quantity is produced. By the end of the second day the gas 

 formation is nearly at an end. The total amount which collects in the 

 closed branch of the fermentation tube is equivalent to about one-half 

 of the capacity of this branch. The gas set free is composed of CO^ and 

 an explosive gas which consists largely of H. The ratio of CO, to H in 

 the fermentation tube is approximately as i :2. The reaction of the liquid 

 becomes strongly acid, which condition checks the multiplication of the 

 bacteria. 



Gas is not produced in bouillon containing lactose or saccharose. 

 These sugars are not fermented. Alkaline cultures containing them 

 become more strongly alkaline as the growth continues. 



Thermal reactions. — This organism grows very feebly at a tem- 

 perature of 20° C. It will not thrive at a temperature above 43° C. It 

 is destroyed when exposed to moist heat at 58° C. for 10 minutes. 



Disinfectants. — This organism is destroyed after an exposure for 10 

 minutes or less in the following solutions: 



Carbolic acid, i per cent. Hydrochloric acid, 1-5 of i per cent. 

 Sulphuric acid, 1-20 of i per cent. Sulphate of copper, 1-4 of i per cent. 

 Formalin, i to 2,000. Trikresol, 1-2 of i per cent. 



Lime is also a good disinfectant when used in preparations contain- 

 ing about I per cent CaO. 



Drying. — This bacillus resists drying for a variable length of time, 

 according to the amount of protection it has. In a drop of a bouillon 

 culture dried on a cover-glass and kept under bell jars, the vitality is 

 retained for from 5 to 8 days. In bits of animal tissue containing the 

 bacilli, the vitality is retained for from 20 to 40 days, according to the 

 quantity of tissue taken. 



Pathogenesis. — Subcutaneous injections of from i to 3 c. c. rarely 

 produce fatal results in swine. An intravenous inoculation of 5 c. c. 

 usually produces a septicaemia. With smaller doses the "button 

 ulcers," characteristic of hog cholera, have been produced (Welch). 

 By feeding pigs with pure bouillon cultures the intestinal lesions, typical 

 of hog cholera, have also been obtained (Smith). 



Rabbits inoculated subcutaneously with o. i c. c. of a bouillon cul- 

 ture die in from 5 to 8 days. The essential lesions consist of necrotic 



