x FOREWORD 



obscured in a cloud of theory. The treatment was haphazard, 

 partly the outcome of experience, partly based upon false 

 theories of the cause of the disease. This may be said to have 

 been the sort of knowledge possessed by the profession until 

 men began to study the "seats and causes" of disease, and to 

 search out the changes inside the body, corresponding to the 

 outward symptoms and the external appearances. Morbid 

 anatomy began to be studied, and in the hundred years from 

 1750 to 1850 such colossal strides were made that we knew 

 well the post-mortem appearances of the more common 

 diseases; the recognition of which was greatly helped by a 

 study of the relation of the pathological appearances with the 

 signs and symptoms. The 19th century may be said to have 

 given us an extraordinarily full knowledge of the chang 

 which disease produces in the solids and fluids of the body.j 

 Great advances, too, were made in the treatment of disease. 

 We learned to trust Nature more and drugs less; we got rid 

 (in part) of treatment by theory, and we d to have a 



drug for every symptom. But much treatment was, and ^t ill 

 is, irrational, not based on a knowledge "1" the cause of the 

 disease. In a blundering way many important advances were 

 made, and even specifics were discovered -cinchona, for 

 example, had cured malaria for a hundred and fifty years 

 before Laveran found the cause. At the middle of the last 

 century we did not know much more of the actual causes of 

 the great scourges of the race, the plagues, the fevers and the 

 pestilences, than did the Greeks. Here comes in Pasteur's 

 great work. Before him Egyptian darkness; with his advent 

 a light that brightens more and more as the years give us ever 

 fuller knowledge. The facts that fevers were catching, that 

 epidemics spread, that infection could remain attached to 

 particles of clothing, etc., all gave support to the view that 

 the actual cause was something alive, a contagium civum. It 

 was really a very old view, the germs of which may be found 

 in the Fathers, but which was first clearly expressed — so far 

 as I know — by Frascastorius, a Veronese physician in the 

 16th century, who spoke of the seeds of contagion passing from 



