APPENDIX E. 



On the ' Germ- theory ' in relation to Epidemic and * specific ' 

 Contagious Diseases *. 



IN medicine, even more than in other less complex 

 sciences, it is well that imperfectly established general doc- 

 trines should be, from time to time, tested by the light of 

 more recently acquired facts. Practice necessarily follows 

 along the paths indicated by theory, and therefore it is in 

 many cases all-important, even from a practical point of 

 view, that true theories should be arrived at. The wider the 

 applications of the theory, the greater is the necessity that 

 it should be sound, and based upon the best knowledge of 

 the time. 



I have determined to lay before you some considerations 

 touching the nature and origin of epidemic and so-called 

 ' specific' contagious diseases ; and you will be impressed with 

 the vast importance of the subject when you learn that nearly 

 one-fourth of the total number of deaths occurring in Great 

 Britain are due to these affections. As the Registrar- General 

 has aptly pointed out : ' Diseases of this class distinguish one 

 country from another one year from another; they have 

 formed epochs in chronology ; and, as Niebuhr has shown, 

 have influenced not only the fall of cities, such as Athens 



1 Being the Inaugural Address in the Faculty of Medicine of University 

 College, which was delivered on October 2nd, 1871. The first and last 

 paragraphs have been omitted, whilst explanatory notes have been added. 



