TEACHING OF PHYSIOLOGY AND PUBLIC HEALTH. 33 



addition of lime juice to the food of every sea-going vessel 

 precluded the possibility of this sickness. 



Another cause of great mortality was repeated out- 

 breaks of jail fever in the prisons of the country. This 

 disease was frequently carried from the prisons to the outer 

 world. It was later recognized as the typhus fever of 

 to-day. It was due to the careful observation of John 

 Howard that this disease was traced to filth and over- 

 crowding. Reforms based upon this have made jails 

 healthier than many homes, and this disease one of the 

 rarest occurrence. 



Then, in 1796, came the discovery of Edward Jenner 

 that smallpox might be prevented by the process of vacci- 

 nation. While the absolute validity of vaccination is still 

 questioned by some people to-day, there is no doubt about 

 the fact that the mortality due to this disease has been 

 many times reduced by this process. 



THE SCIENCE OF BACTEEIOLOGY. 



It was reserved to our own day to give us a scientific 

 insight into the cause of disease. The science of bacteri- 

 ology is a product of the last few years. At first a small 

 branch of the science of botany, bacteriology has com- 

 manded more and more attention; has ramified in wider 

 and wider directions until now it has the dignity of a dis- 

 tinct science ; and there are perhaps few subjects of study 

 which are to-day being pursued with such an avidity, and 

 in which the results obtained have proved of such unspeak- 

 able worth. An elementary understanding of the more 

 important conceptions of bacteriology is necessary to a 

 proper appreciation of hygienic laws. No one any longer 

 questions the cause of all our contagious and infectious 

 diseases. It is a matter of every-day comment to speak of 

 the various germs producing respectively the various con- 

 tagious diseases. A short summary of the growth of this 

 science may be a matter of interest. 



