DISEASES FROM MICRO-ORGANISMS. 129 



tain, however, whether these organisms are present as 

 the actual cause of the disease, or are only secondary 

 invaders. 



MUMPS. 



This is an acute infectious disease affecting- the 

 salivary glands in infants and young adults. It is 

 contagious, being spread directly from one patient to 

 another. The infectious agent is unknown. 



TYPHUS FEVER. 



While characteristic bacilli have been described in 

 the blood of patients sick with this disease, efforts to 

 cultivate them have not been successful. The infection 

 can be transmitted to monkeys by injecting them with 

 the blood of patients. The infection can be carried by 

 the body louse (Pedkulus vestimentorum) , 



