MICROBIAL DISEASES OF MAN AND ANIMALS. 659 



of material from an infected spinal cord, but attempts at infection through 

 feeding have been unsuccessful. The virus appears to be eliminated from 

 the body through the nasal mucous membranes. 



It appears probable that one attack of the disease protects from a 

 second attack. No cases of a second attack have been reported. Further- 

 more, monkeys which have recovered from the infection appear to be en- 

 tirely immune as shown by Flexner. Active immunity in monkeys has 

 been established by repeated infections of gradually increased amounts 

 of the virus. The blood of human beings and of monkeys that have re- 

 covered from an attack of the disease is capable of neutralizing a certain 

 amount of the virus. This protective quality of the blood serum may be 

 increased by repeated inoculations of virus, and infection in monkeys can 

 be prevented by injecting simultaneously the virus into the brain and the 

 serum into the sub-arachnoid space. The serum treatment of this disease 

 is, however, not developed to such a state that it can be regarded as of 

 practical use. 



LOUPING ILL TREMBLING IN SHEEP.* 



This disease is known only in Scotland and is essentially a disease of 

 sheep. It is characterized by a variety of nervous phenomena, such as 

 trembling, irritabilty, and convulsive movements, which are followed later 

 by partial or complete paralysis. The chief lesions are found in the men- 

 ingeal membranes. This disease is supposed to be transmitted by ticks, 

 not the wingless fly which is generally called a "sheep tick" in the United 

 States, but true ticks, belonging to the genus Ixodes. The specific 

 microorganism has not been discovered. 



PELLAGRA, f 



Pellagra is a disease of man characterized by the annually recurring 

 manifestation, each spring or autumn or both, of erythema on the backs 

 of the hands and forearms and sometimes on the face and neck, feet and 

 ankles, coupled with digestive disorder, and more or less well-marked 

 mental disturbances. During the winter the signs of the disease usually 

 disappear. 



At present there are two main groups of theories concerning the caus- 

 ation of pellagra, each of which includes a multitude of hypotheses. 

 According to one group of theories pellagra is a food poisoning due to eat- 



* Prepared by M. Dorset. 



t Prepared by W. J. MacNeal. 



