PREVENTION OF EPIDEMICS. 17 



only a little less susceptible than he who has never been vaccin- 

 ated at all." * 



Each of these infectious fevers grows and spreads by conditions 

 peculiar to itself, which depend, to a considerable ext ^nt, on the 

 length of its incubation period. 



The two first of these diagrams show sufficiently well the 

 manner in which the recent epidemics in Edinburgh of typhus, 

 typhoid, and scarlet fevers began, and spread; as also nearly the 

 numbers affected, and the duration of the epidemics. 



We have now to speak of 



THE MEANS NECESSARY FOR THE CONTROL AND 

 PREVENTION OF INFECTIOUS DISEASES. 



The instructions intended for your guidance in emergencies 

 \vhich I have drawn up, based on my lecture,! are, I understand, 

 already in your hands ; and I am thus so far relieved from many 

 details, which it would otherwise have been desirable for me to 

 touch upon. I will ask you then to hold that part of my lecture 

 as read; and I will now proceed in a few brief sentences to 

 enumerate those measures for the effectual control and preven- 

 tion of epidemic disease which I consider to be necessary. 



Firstly, We must aim at the promotion of cleanliness of every 

 description, by the employment of those legal powers contained 

 in public health enactments, which are amply sufficient for the 

 purpose if carried out. 



Secondly, At placing all building operations such as the con- 

 struction of houses, selection of healthy sites, house and general 

 drainage under strict sanitary inspection and supervision. 



Thirdly, At preventing over-crowding, alike in dwellings or in 

 districts. This measure comprehends the constant inspection of 

 houses, the width of streets, the height of houses, the removal 

 of old and insanitary dwellings, the promotion of open spaces, 



* Lectures on the "Prevention and Control of Infectious Diseases," by 

 Dr J. B. Russell, 

 t See Appendix. 



