THE LIBERTY OF SCIENCE IN THE MODERN STATE. 301 



duty to infer, in the sense of an inductive exten- 

 sion of our knowledge, that all contagia and 

 miasmata are living organisms. Indeed, gentle- 

 men, I will admit that this conception is an ex- 

 tremely probable one. Even those investigators 

 who have not yet gone so far as to regard con- 

 tagia and miasmata as living beings have yet al- 

 ways said that they resemble living beings very 

 closely, that they have properties which we 

 otherwise know in living beings only, that they 

 propagate their kind, that they increase and are 

 regenerated under special circumstances, that, 

 indeed, they appear like real organic bodies — 

 these men, nevertheless, have waited, and rightly, 

 until the existence of infective organisms was 

 proved. Thus does prudence still counsel re- 

 serve. 



We must not forget that the history of science 

 presents a number of facts which teach us that 

 phenomena which are very closely allied to one 

 another may occur under very unlike conditions. 

 When fermentation was traced to the presence 

 of certain fungi, when it was known that its 

 beginning is closely connected with the develop- 

 ment of certain species of fungi, the inference 

 was easily drawn that all processes related to 

 fermentation happen in the same way; I mean 

 all those processes which are comprised under 

 the name of " catalytic," and which occur so fre- 

 quently in the human and animal body as well as 

 in plants. There were, indeed, some scientific 

 men who imagined that digestion, which is one 

 of the processes which closely resemble those of 

 fermentation, was brought about by certain fungi 

 which occur frequently (in the special case of cat- 

 tle the question has been practically discussed), 

 and which were supposed to cause digestion in 

 the stomach in the same way as the ferment fungi 

 cause fermentation elsewhere. We now know 

 that .the digestive juices have absolutely nothing 

 to do with fungi. Much as they may possess 

 catalytic properties, we are yet certain that their 

 active substances are chemical bodies which we 

 can extract from them, which we can isolate from 

 their other component parts, and which we can 

 cause to act in the isolated state free from any 

 admixture of living organisms. The human sali- 

 va has the property of very rapidly converting 

 starch and dextrine into sugar, and every time 

 we eat bread, " sweet " bread is formed in the 

 mouth ; nevertheless we have here no fungus, no 

 ferment organism, but only certain chemical sub- 

 stances which produce transformations very simi- 

 lar to those produced within the fungi. Here, 

 then, we see two processes that closely resemble 



one another brought about in very different ways, 

 the one in the interior of the ferment fungus, the 

 other in the digestive organs of man ; in one case 

 the process is connected with a definite vegetal 

 organism, in the other case it takes place without 

 any such organism, and simply through a liquid. 



I should consider it a great misfortune if we 

 were not to continue, in the same way as I have 

 done now, to examine in each single case whether 

 the hypothesis we frame, the idea which we form, 

 and which may be highly probable, is really true, 

 whether it is justified by facts. Here I would re- 

 mind you that there are cases also among the in- 

 fectious diseases where most undoubtedly a simi- 

 lar contrast exists. My friend Herr Klebs will 

 no doubt pardon me if I, even now, in spite of 

 the recent progress which the doctrine of infective 

 fungi has made, still maintain my reserve, and 

 only admit that fungus which has been proved by 

 demonstration, while I deny all the other fungi as 

 long as I do not hear of facts which attest them. 

 Among infectious diseases there is a certain group 

 which are caused by organic poisons — I will only 

 mention one of them, which, according to my 

 opinion, is very instructive — I mean the poison- 

 ing by a snake-bite, a very celebrated and most 

 remarkable form. If we compare this kind of 

 poisoning with those kinds which are generally 

 called infectious diseases (infection means little 

 else than poisoning), we must admit that there 

 exists the closest analogy between the two in the 

 course they usually take. As far as the succession 

 of the symptoms is concerned, there is nothing to 

 negative the hypothesis that the ensemble of phe- 

 nomena consequent on snake-bite was caused by 

 fungi entering the body and producing certain 

 changes in different organs. Indeed, there are 

 some processes, septic processes, for instance, 

 where just such phenomena occur, and it is cer- 

 tain that some forms of poisoning by snake-bite 

 resemble some forms of septic infection as much 

 as one egg resembles another. And yet we have 

 not the least cause to suspect an importation of 

 fungi into the body in the case of snakebite, 

 while in the case of septic processes we, on the 

 contrary, acknowledge and recognize this impor- 

 tation. 



The history of natural science has numerous 

 examples, which ought always to cause us more 

 and more to restrict our doctrines absolutely to 

 that domain only in which we can actually prove 

 them, and not by way of induction to proceed so 

 far as to extend doctrines immeasurably which 

 have only been proved for one or more cases. 

 Nowhere is the necessity of such restriction more 



