34 6 PATHOGENIC BACTERIA. 



tion and cultivation by the usual plate method are apt to 

 fail, because the numerous other organisms in the material 

 grow much more rapidly. 



The best method of isolation seems to be the use of an 

 animal reagent. It has been said that glanders princi- 

 pally affects horses and asses. Recent observations, how- 

 ever, have shown the goat, cat, hog (slightly), field-mouse, 

 wood-mouse, marmot, rabbit, guinea-pig, and hedgehog 

 all to be susceptible animals. Cattle, house-mice, white 

 mice, and rats are immune. 



The guinea-pig, being a highly susceptible as well 

 as a readily procurable animal, naturally becomes the 

 reagent for the detection and isolation of the bacillus. 

 When a subcutaneous inoculation of some glanders pus 

 is made, the disease can be observed in guinea-pigs 

 by a tumefaction in from four to five days. Somewhat 

 later this tumefaction changes to a caseous nodule, which 

 ruptures and leaves a chronic ulcer with irregular mar- 

 gins. The lymph-glands speedily become involved, and 

 in a month to five weeks signs of general infection are 

 present. The lymph-glands suppurate, the testicles un- 

 dergo the same process, and still later the joints exhibit 

 a suppurative arthritis containing the bacilli. The ani- 

 mal finally dies of exhaustion. In guinea-pigs no nasal 

 ulcers form. In field-mice, which are even more suscepti- 

 ble, the disease is much more rapid. No local lesions 

 are visible. In two or three days the animal seems un- 

 well, the breathing is hurried, it sits still with closed 

 eyes, and without any other preliminaries tumbles over 

 on its side, dead. 



From the tissues of the inoculated animals the pure 

 cultures are most easily made. Perhaps the best places 

 to secure the culture are from softened nodes which have 

 not ruptured or from the suppurating joints. Strauss 

 has, however, given us a method which is of great use, 

 because of the short time required. The material sus- 

 pected to contain the glanders bacillus is injected into 

 the peritoneal cavity of a male guinea-pig. In three or 



