THEIR MODE OF ACTION. 405 



cause an immediate cessation of the functions of 

 the most important organs, if they continue in their 

 action, although in an abnormal condition, conval- 

 escence ensues. In this case the products of the 

 transformations still existing in the blood are used 

 for assimilation, and at this period secretions of a 

 peculiar nature are produced. 



When the constituent removed from the blood is 

 a product of an unnatural manner of living, or when 

 its formation takes place only at a certain age, the 

 susceptibility of contagion ceases upon its disap- 

 pearance. 



The effects of vaccine matter indicate, that an 

 accidental constituent of the blood is destroyed by 

 a peculiar process of decomposition, which does not 

 affect the other constituents of the circulating fluid. 



If the manner in which the precipitated yeast of 

 Bavarian beer acts (page 350) be called to mind, 

 the modus operandi of vaccine lymph can scarcely 

 be matter of doubt. 



Both the kind of yeast here referred to and the 

 ordinary ferment are formed from gluten, just as the 

 vaccine virus and the matter of smallpox are pro- 

 duced from the blood. Ordinary yeast and the virus 

 of human smallpox, however, effect a violent tumul- 

 tuous transformation, the former in vegetable juices, 

 the latter in blood, in both of which fluids respec- 

 tively their constituents are contained, and they are 

 reproduced from these fluids with all their character- 

 istic properties. The precipitated yeast of Bavarian 

 beer on the other hand acts entirely upon the sugar 

 of the fermenting liquid and occasions a very pro- 

 tracted decomposition of it, in which the gluten 

 which is also present takes no part. But the air 

 exercises an influence upon the latter substance, and 

 causes it to assume a new form and nature, in con- 

 sequence of which this kind of yeast also is repro- 

 duced. 



The action of the virus of cow-pox is analogous 

 to that of the low yeast ; it communicates its own 



