MEDICINE 573 



3. An infected population succumbs far more rapidly to 

 a severe epidemic if fresh susceptible individuals gain access to 

 it in considerable numbers than if it remains isolated. 



It is anticipated that these findings may be applied to the 

 solution of disease problems in the cattle industry at an early 

 date. Another interesting piece of work which is discussed in 

 the report is that of Haldane and Collis on rock-dust in relation 

 to tuberculosis. The work of Gye in this connection appears 

 to leave little doubt that silica plays a very big part in the 

 incidence of tubercle, for he found that if silica was added to 

 injections of tubercle bacilli given to insusceptible animals acute 

 tuberculosis often resulted. The work of Holford Ross on 

 printers' phthisis deserves mention in this connection. He has 

 recently shown that dust is carried in printing offices on the 

 fine particles of cotton fluff which are to be found in the air. 



