96 FEBMENTS AND MICRO-PARASITES. 



parasites, and the number of sceptics and opponents 

 have diminished from year to year. It is true that the 

 difficulty of these investigations, which only permitted 

 an extremely slow advance, and one but little satisfying 

 to the earnest desire for rapid enlightenment, led some 

 observers to overstep the limits of exact investigation, 

 and to attach too far-reaching speculations to the results 

 of the experiments : it was natural and pardonable that 

 at times conclusions as to the origin of the diseases 

 were drawn from the mere presence of micro-organisms 

 in the dead bodies or in pathological secretions, and 

 that these organisms were at times prematurely and 

 erroneously proclaimed to be the exciting agents of the 

 disease. On the other hand many investigators recog- 

 nised that it was only by detailed study of the different 

 forms of micro-organisms which came under observation, 

 by the investigation of the conditions and results of their 

 life, by improvement of the methods of microscopical 

 observation, and by faultless experiments on animals that 

 a basis could be obtained on which an accurate and sure 

 insight into the r6le of the parasitic agents of disease 

 could be founded. Based on the recognition of these 

 facts the more recent methods of mycological investiga- 

 tions were built up. Before it was possible to obtain 

 exact and unequivocal results it was necessary to have 

 Pasteur's and Cohn's systematic cultivations, Koch's 

 method of microscopical investigation and pure cultiva- 

 tion of the fungi, Weigert's and Ehrlich's valuable 

 researches on the employment of dyes for demonstrating 

 the micro-organisms, Brefeld's contributions to the 

 methodical study of the lower fungi, and Nageli's work 

 as to the conditions of life and the tissue change of the 

 lower fungi. 



The objections which are raised against the parasitic 

 theory are derived almost entirely from former times, 

 and are now scarcely heard. Apart from the views of 

 some stubborn adversaries, who only believe the contra- 

 dictory results of their own experiments, the doubts raised 

 against the recent work on tee parasitic theory have to 

 do chiefly with individual cases and special diseases. 



