BACTERIA AS THE CAUSES OF DISEASE. 79 



ducing fermentation processes, and Hallier, who was well 

 acquainted with these researches, concluded that if the yeast 

 cells were part of a developmental cycle, the bacteria might 

 also be taken to represent only short resting stages of the 

 same or similar cycles. This was an especially seductive 

 theory, as up to this time the origin of these minute forms 

 had, as we have seen, been enshrouded in mystery, and had 

 provided matter for the keenest controversy. 



A lady, Johanna Liiders, was firmly convinced that the 

 lower bacteria and yeasts developed in some way or other 

 from the individual parts of the mycelium of certain fungi, 

 or from their spores. Her observations were repeated, and 

 there was a general concurrence of opinion that the bacteria 

 were derived in some way from fungi and from other higher 

 plant forms. 



Hallier, with his isolation apparatus, which consisted 

 really of Schwann's apparatus, to which an air-pump and a 

 cotton wadding filter were added, and his cultivation ap- 

 paratus, which corresponds practically to the potato-jar of 

 to-day, with water to take the place of bichloride of mercury 

 solution, came to the conclusion that the cause of almost 

 every infective disease was to be looked for in bacteria, 

 monads, and cocci, which in their turn were nothing but 

 forms produced during the developmental cycle of one or 

 other of the fungi aspergillus, penicillium, mucor, &c. 



Loffler says, in summing up the results of Hallier's re- 

 searches, " He put forward the hypothesis that all contagia and 

 miasmata are the products of fungi or algae which alone, on 

 account of their small size, are able to pass through the fine 

 capillary vessels, and that it was only necessary, in order to 

 determine the nature of the original cause, first to find out the 

 micrococcus and then to trace it back to the fungus to which 

 it owed its existence." By such new ideas, propounded with 

 such an air of conviction and authority, Hallier made a most 

 profound impression on both the lay and scientific world. 

 The whole system was so simple and clear and every part 

 contributed so easily and naturally to form one harmonious 

 whole ; every assertion was so definitely supported by micro- 

 scopic observation and cultivation experiments that no doubt 

 as to the correctness of the demonstrations seemed to be 

 possible. 



It was a somewhat noteworthy fact, however, that the pern- 



