Nov. 29, 1877] 



NATURE 



93 



and are regenerated under special circumstances, that, indeed, 

 they appear like real organic bodies, — these men, nevertheless, 

 have waited, and rightly, until the proof of their being living 

 organisms was furnished. And thus caution commands reserve 

 even now. 



We must not forget that the history of science presents a number 

 of facts which teach us that very similar phenomena may happen 

 in a very different manner. When fermentation was reduced to 

 the presence of certain fungi, when it was known that its begin- 

 ning was closely connected with the development of certain 

 species of fungi, then it w as really very obvious to imagine 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 frequently 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 the fermentative ones, was 

 brought about by certain fungi which occur frequently (in the 

 special case of cattle the question has been practically discussed), 

 and which were supposed to cause digestion in the stomach in 

 the same way as the fermentation fungi cause fermentation 

 elsewhere. We now know that the digestive juices have 

 absolutely nothing to do with fungi. Much as they may possess 

 catalytic propertie-:, 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, an i which we can 

 cause to act in the isolated state free from any admixture of living 

 organisms. If the human saliva has the property of being able 

 to change starch and c'extrine into sugar ita the shortest time, and 

 if every time we eat bread this new formation of "sweet" 

 bread takes place in our mouth, then no fungus takes part in 

 this nor any fermentation organism, but there are chemical 

 substances which, much in the same way as it happens in 

 the interior of the fungus, bring about chemical change in 

 matter. We see, therefore, that two processes which are 

 extremely similar, the one in the interior of the feraieiitation 

 fungus and the other in the process of human digestion, are 

 brought about in different ways ; the same process in the one 

 instance is connected with a certaia vegetable organism, while in 

 the other it takes place without any such organism and simply 

 through a liquid. 



I should consider it a great misfortune if we were not to con- 

 tinue in the same way as I have done now, to examine in each 

 single case whether the supposition which we make, the idea 

 which we have formed and which may be highly probable, is 

 really true, whether it is justified by facts. With regard to this 

 I would remind you that there are cases also amongst the 

 infectious diseases where most undoubtedly a similar contrast 

 exists. My friend. Prof. Klebs, will no doubt pardon me if I, 

 even now, in spite of the recent progress which the doctrine of 

 infecting fungi has made, still remain in my reserve, and that I 

 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. Amongst 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 poisoning by a snake-bite, a very cele- 

 brated and most remarkable form. If this kind of poisoning is 

 compared with those kinds of poisoning which are generally 

 called infectious diseases (infection does not signify much else 

 than poisoning), then we must admit that in the courses both 

 cases generally take the greatest analogies exist. With regard to 

 the course of the illness nothing would oppose the supposition 

 that the total sum of pheiaomena which occur in a human body 

 after a snake-bite, were caused by fungi which entered the body 

 and which produced certain changes in different organs. Indeed 

 we know certain processes, septical ones, for instance, wheie 

 phenomena of a completely similar nature occur, and it 

 cannot be denied that certain forms of poisoaing by snake-bite 

 resemble certain forms of septical infection ai 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 

 snake bite, while in the case of septic processes we, on the 

 contrary, acknowledge and recognise this importation. 



The history of our natural science has numerous examples, 

 which ought always to cause us more and more to confine the 

 validity of our doctrines in the most stringent manner to that 

 domain only in which we can actually piove them, and that we do 

 not by way of induction, proceed so far as to extend doctrines 

 immeasurably which have only been proved for one or several 

 cases. Nowhere the necessity of such a restriction has become 



more apparent than on the field of the theory of evolution. The 

 question of the first origin of organic beings, this question which 

 also forms the basis of progressive Darwinism, is an extremely 

 old one. It is not known at all who first tried to find the 

 different solutions for it. But if we remember the old popular 

 doctrine, according to which all possible beings alive, animals 

 and plants, could originate from a clod of clay — from a little 

 clod under circumstances — then we ou^ht to remember at the 

 same time that the celebrated doctrine of goteratio ceqiiivoca, 

 of epigenesis, is closely connected with it, and that it has 

 been a common idea for thousands of years. Now with 

 Darwinism the doctrine of spontaneous generation has been 

 taken up again, and I c mnot deny that there is something very 

 seductive in the idea of closing the theory ( f descent in this way, 

 and, after the whole series of living forms has been constructed, 

 from the lowest protozoa upwards to the highest human organism, 

 to connect this long series v/ith the inorganic world as well. 

 This corresponds with that direction to generalise, which is so 

 entirely human, that it has found a place in the speculation of man- 

 kind at all times, backwards to the most obscure periods. We have 

 the undeniable desire not to separa'e the organic world from 

 the universe, as a something which is divided from it, but 

 rather to insure its connection with the universe. In this sense it 

 is pacifying if one can say, the atom-group carbon and company 

 — this is perhaps speaking too collectively, but ye: it is correct, 

 since carbon is to be the essential element — therefore, this asso- 

 ciation, carbon and company, has at some special time separated 

 itself from the ordinary carbon and founded the first plastxdule 

 under special circumstances, and continues to found it in the pre- 

 sent. But in the face of this we must mention that all real scientific 

 knowledge of the pheaomena of life has proceeded in an opposite 

 direction. We date the beginning of our real knowledge of the 

 development of higher organisms from the day when Harvey 

 pronounced the celebrated phrase, " Omne vivum ex ovo," every 

 living being comes from an egg. This phrase as we now know, 

 is incorrect in its generality. To-day we can no longer recognise 

 it as a fully justified one ; we know that, on the contrary, a 

 whole number of generations and propagations exist without ova. 

 From Harvey down to our celebrated friend Prof, von Siebold, 

 who obtained the general recognition of parthenogenesis, there 

 lies a whole series of increasing restriction?, all of which prove 

 that the phrase, " Omne vivum ex ovo " was incorrect speaking in 

 a general sense. Nevertheless, it would bathe highest ingratitude 

 if we were not to acknowledge that in the opposition, which 

 Harvey assumed against the old gemratio crquivoca, the greatest 

 progress was made which has been made by science in this 

 domain. Later on a great number of new forms were known, in 

 which the propagation of the different kinds of living beings is 

 going on, in which new individuals originate— direct separation, 

 gemmation, metagenesis. All these forms, parthenogenesis 

 included, are data which have caused us to give up every single 

 (cinheitlicke) system for the generatioa of organic individuals. 

 In place of a single schema we now have a variety of data ; we 

 have no uniform system left by which we could explain once for 

 all how a new animal being begins. 



Generatio aquivoca, which has been disputed and refuted 

 as many times, nevertheless faces us again and again. It is 

 true that not a single positive fact is known which proves that 

 generatio wquivoca has ever occurred, that spontaneous genera- 

 tion has ever taken place in such a way that inorganic masses, 

 let us say the association carbon and company, have ever spon- 

 taneously developed into an organic substance. Nevertheless, I 

 admit that if we indeed want to form an idea how the first 

 organic being could have originated by itself, nothing remains but 

 to go back to spontaneous generation. This is clear. If I do 

 not want to suppose a creation-theory, if I do not want to believe 

 that a special creator existed, who took the clod of clay and blew 

 his living breath into it, if I want to form some conception in my 

 own way, then I must form it in the sense of generatio tcquivoca, 

 Tertium tton datur. Nothing else remains if once we say " I do 

 not admit creation, but I do want an explanation." If this is the 

 first thesis, then v,-e must proceed to the second and say " Ergo, 

 I admit generatio csquiuoca." But we have no actual proof for 

 it. Nobody has ever seen generatio crquivoca occurring in 

 reality, and everyone who maintaii>ed that he had seen it, has 

 been refuted, not by theologians indeed, but by naturalists. I 

 mention this, gentlemen, in order to let our impartiality appear 

 in the riglit light, and this is very necessary at times. We 

 always have our weapons in ourselves and about us, to fight 

 against that which is not justified. 



I therefore say that I must admit the theoretical justification 



