22 DEVELOPMENT OF THE GERM THEORY. 



von Ziemssen's Cyclopaedia of Medicine^ published in 1875, ^^ ^^^ 

 Liebermeister, in his introduction to Infections Diseases^ recording 

 nearly the same views without being able to bring forward much 

 more actual proof of them. He refers to the hypotheses produced 

 up to our time by both the learned and unlearned, most of them 

 not very poetic, but about as vague as the descriptions of the old 

 poets who wrote of the "death-dealing shafts of Apollo;^' or as 

 the views advanced in a well-known novel, where cholera is asso- 

 ciated with the footsteps of the wandering Jew. He mentions that 

 in all great epidemics, since the time of the Athenian plague, 

 there has been a revival of the popular notion that the wells were 

 poisoned, and says that this idea had certainly the advantage over 

 most of the hypotheses which were clothed in scientific guise, 

 inasmuch as it supposed a real cause. 



Referring to the theory of contagium vivum, and alluding to 

 its antiquity, he shows how, in later times, it had been maintained 

 with decided ill luck, 'i'he statements of the first observers who 

 believed that they had found the organisms that were at the basis 

 of all epidemic diseases, were soon recognised as too hasty or 

 overdrawn, the animalculae of smallpox, of cholera, and of choler- 

 aic Tungi, proved to be quite common infusorial organisms, such 

 as can be found in all decomposing substances. About the middle 

 of the present century, the judgment of condemnation of this 

 theory was almost unanimous ; it has been regarded pretty gene- 

 rally as an unreal, unscientific play of fancy. Among the medical 

 authorities^ Henle was probably the last who elaborated the theory 

 of a contagium vivum. This he did in 1853, with as much 

 modesty as thoroughness, though even as early as 1840 he had 

 maintained it with convincing logic. 



Liebermeister gives very fully his own reasons for maintaining 

 the correctness of the theory : — New investigations on the appear- 

 ance, mode of propagation, and significance of low organisms \ 

 the fact that the poisons of infectious diseases can reproduce 

 themselves to an unlimited extent; that with a minimum quantity 

 of vaccine virus we can vaccinate a child, from this child ten, and 

 so on ad iiifinitwn ; as with vaccine virus so with variola, measles^ 

 scarlet fever, typhus, etc., the poison can be multiplied to an 

 endless extent. 



