210 OVINE CASEOUS LYMPH-ADENITIS 
and does not produce spores. It develops readily on agar when this 
medium is inoculated from the caseous material from the affected 
glands. It is pathogenic for mice, guinea pigs, rabbits and swine. 
The organism isolated by Gilruth seems to have been more virulent 
than the one described by Nérgaard and Mohler. According to 
Carri and Bigoteau it produces a strong toxin. 
Nocard and Glasser found that lambs could be infected by both 
inhalation and ingestion of the organism. The natural mode of 
infection is not known but it is believed that the channels of infection 
are the digestive and respiratory tracts and the umbilicus. 
Symptoms. In the majority of cases no symptoms of any import- 
ance are observed in the affected animals during life. The course 
Fic. 47. THE LEG OF A RABBIT SHOWING ENLARGED GLANDS AFTER INOCULATION 
WITH THE BACTERIUM OF PREISZ (NGrgaard and Mohler). 
of the disease is that of a chronic affection and the pathological 
changes develop so slowly that no general or local interference with 
the health is observed in sheep that are bred and raised for mutton 
and are marketed before they are two years old. Only in older sheep 
does it advance to a degree to be clinically recognizable without the 
aid of manipulation. The superficial] glands most often involved 
are the precrural and the subscapular which in some cases become so 
enlarged as to interfere with locomotion. The animals thus affected 
may appear to be in perfect health although they may show a certain 
degree of unthriftiness or emaciation. In advanced cases the lesions 
may be disseminated through metastasis to the principal organs of the 
body. In such cases the disease may assume the appearance of 
chronic broncho-pneumonia or pleurisy, with occasional cough, slight 
dyspnea, emaciation and anemia. The course of the disease is very 
slow and fatal results are rare. 
Morbid anatomy. The principal lesions are confined, according to 
the various descriptions, to the lymphatic glands. In many cases 
