BIOLOGY OF BACTERIA. 61 



Production of Enzymes by Bacteria. — Some of these 

 have already been mentioned, as those which coagulate 

 milk, dissolve gelatin, etc. There are, however, many 

 others which have interesting actions upon animal and 

 vegetable substances. 



Knowledge upon the subject is just becoming systema- 

 tized, one of the best works being that of Emmerich and 

 Low, 1 who, observing that in old cultures of Bacillus 

 pyocyaneus the bacteria became transformed into a gelat- 

 inous mass, were led to experiment with concentrations 

 of old cultures. For this purpose the well-grown and 

 degenerating cultures were condensed to ^ volume in 

 a vacuum apparatus, when their bacteriolytic powers 

 were found to be much increased. Emmerich and Low 

 were subsequently able to precipitate from the culture an 

 enzyme, which they called Pyocyanase, and reached the 

 rather hasty inference that the cessation of growth of 

 bacteria in cultures depends upon the generative enzymes; 

 that the enzymes destroy the dead bacteria; that enzymes 

 will kill and dissolve living bacteria and destroy toxins, 

 and, therefore, are useful for the treatment of infectious 

 diseases. Further, that the antitoxins are simply the 

 accumulated enzymes which the immunized animals 

 have received during the progress of their treatment, and 

 which, appearing in the serum, produce the effects so well 

 known. 



It is very probable that many of the toxic effects of 

 bacteria and their cultures depend upon the enzymic sub- 

 stances present. 



1 Zeitschrift fur Hygiene, 1899. 



