SILESIAN SOCIETY FOR NATIONAL CULTURE. 207 



This view does not seem to be borne out by the section of 

 another shell which was exhibited, Area naviciila, in whicli the 

 tubuli are always present, forming an integral part; they are 

 disposed in a straight and tolerably regular manner between the 

 ridges of the shell ; moreover, they have neither the irregularly 

 branched structure nor the sporangia. 



SiLESIAN SOOIETT FOE NA.TIONAL CuLTUEE. 



Section of Natural Science. 



Bacteria and their relations to Putrefaction and to Con- 

 tagia. — Professor Cohn delivered a lecture on this subject at the 

 meeting of February 14th. Denoting hj fermentation the decompo- 

 sition of certain non-nitrogenous substances excited by microscopic 

 organisms, he described the analogous decompositions of nitro- 

 genous, and especially albuminous substances, as putrefaction. 

 While the phenomena of fermentation have been most elaborately 

 and fruitfully studied of late years by Pasteur, the process of putre- 

 faction has been till now neglected by investigators, and especially 

 by chemists. Cohn's own investigations have given the following 

 results : — 1. All putrefaction is accompanied by the development 

 of bacteria ; it is wanting, if the access of these is prevented ; it 

 commences as soon as bacteria are present, even in the smallest 

 number ; it proceeds in the same ratio as these smallest of all 

 organisms multiply ; and with the completion of putrefaction 

 ceases also the multiplication of the bacteria, which are then pre- 

 cipitated as a powder, or else in gelatinous lumps (Zooglea), just as 

 yeast precipitates in completely fermented sugar solutions. 



There can be accordingly no doubt that bacteria are essential 

 factors in putrefaction just in the same way as yeast fungi have 

 been proved to be in fermentation. Moreover, the bacteria are the 

 only organisms wbich appear exclusively during putrefaction, and 

 under all circumstances, and when the access of alien germs pre- 

 vented ; they are therefore excitors of putrefaction {saprogenous 

 bodies) while the other organisms developed in putrefying sub- 

 stances, the mould fungi and infusoria, are only to be regarded as 

 accompaniments of putrefaction {saprophilous bodies). There is 

 no genetic relation between bacteria and mould fungi as often sup- 

 posed. 



2. The question, how the bacteria which excite putrefac- 

 tion find their way into nitrogenous substances is generally 

 answered by supposing that their germs come from the air with 

 the dust. But this hypothesis, supported alike by the experiments 



