THE GERM THEORY. 



man at the end of life ; but their direct eruptions are excessively 

 fatal to men in the prime and vigour of age." These weighty 

 words of the two greatest living authorities on this subject 

 ought to be well pondered. 



Mr Simon reckons the deaths from these diseases at 120,000 in 

 England and Wales alone. If we add those in Scotland and 

 Ireland, from the same causes, the total mortality is over 150,000, 

 every one of which is a needless death. Does this not strike you 

 as a frightful waste of life 1 If we now compute that each one of 

 these deaths represents, at a moderate estimate, thirty instances in 

 which there is loss of health short of death, the aggregate of need- 

 less death aud suffering becomes perfectly astounding, and affords 

 a sufficiently cogent reason why zymotic diseases are specially 

 singled out to be dealt with by stringent enactments having for 

 their object their prevention, and ultimately total extinction. 



THE GERM THEORY OF INFECTIOUS DISEASES. 



How THEY ORIGINATE. The term Zymotic is applied by those 

 who believe that in these disorders there takes place a process 

 which bears a striking resemblance to that of fermentation. 

 This resemblance was first pointed out by Leibig. Thus, when 

 yeast is added to a solution of sugar, the yeast cells rapidly mul- 

 tiply by feeding on it alcohol and carbonic acid being given 

 off during the process. Yeast, I should tell you, is a rudi- 

 mentary plant composed of cells, which, when placed in a 

 suitable medium, actively multiply, living at the expense of 

 the medium in which they exist, and ultimately changing its 

 character. (See Diagram.) This is fermentation, as it occurs 

 outside of living bodies, and is the starting-point of the idea 

 that germs of different kinds animal and vegetable are the 

 active agents in the production of zymotic diseases. That 

 these germs do exist abundantly in the air, and elsewhere, has 

 been proved by the experiments of many observers, and especially 

 by Pasteur, a French physiologist. [Here describe and show 

 Pasteur's experiments with air and liquids in sealed flasks.] 



