SILESIAN SOCIEl'Y FOR NATIONAL CULTURE. 209 



with ammonium nitrate, glycerin and potassium nitrate, potassium 

 tartrate and potassium nitrate, &c. On the other hand, bacteria do 

 not multiply in ammonium nitrate, potassium tartrate, or solution 

 of urea, but they do in the latter if potassium tartrate be added. 

 As will be taken for granted after the researches of Pasteur, it was 

 necessary in all these experiments to add to the solution a certain 

 quantity of phosphoric acid, sulphuric acid, potash, lime and magnesia. 



4. Since bacteria assimilate nitrogen in the form of ammonia or 

 nitric acid, their work in putrefaction can only be conceived of in 

 the following way : — That they split up the albuminous com- 

 pounds into ammonia which is assimilated, and into other bodies 

 which appear as by-products of putrefaction ; and the nature of 

 the latter is as yet only imperfectly known, though it will certainly 

 be elucidated by the study of the putrefaction of chemical solutions 

 (3). Perhaps it is by means of the ammonia thus set free that 

 the bacteria make insoluble albuminous compounds soluble in putre- 

 faction. Putrefaction is then splitting up of albuminous com- 

 pounds by bacteria, just as alcoholic fermentation is splitting up of 

 sugar by the yeast fungus. 



5. With a certain class of bacteria the products of decomposition 

 are characterised by being coloured. This "pigment-rot" has 

 been previously observed, especially on the surface of boiled potatoes, 

 bread, meat, &c., where purple red gelatinous masses (Monas prodi- 

 giosd) are produced. Yellow and blue pigments have been observed 

 in milk, green in pus, in other cases orange, yellow, brown, and 

 violet pigments. The producers of " pigment-rot " are not the 

 ordinary rod-like or cylindrical bacteria {bacterium termo), but 

 spherical bodies, arranged in pairs, or in beaded chains, or imbedded 

 in mucus, which have no independent movements, and are distin- 

 guished as spherical bacteria or hacteridia. 



Cobn has also succeeded in producing "pigment-rot" in 

 chemical solutions. Solutions of ammonium acetate and potassium 

 tartrate become coloured in a few days, after the addition of a drop 

 of fluid containing bacteria, first greenish, then bluish-green, 

 finally a beautiful blue, like copper sulphate, while there was con- 

 tinually increase of turbidity, caused by cylindrical and spherical 

 bacteria, which at length caused the previously acid reaction to 

 become alkaline. The blue colouring matter is turned red bv acids 

 and blue again by ammonia, and appears to be identical with litmus, 

 which is well known to be also produced by the pigmental putre- 

 faction of colourless extracts of lichens in presence of ammonia. 



6. The presence of bacteria in the blood, or in various secretions, 

 has been lately demonstrated in a number of contagious diseases ; 

 it is in a high degree probable that these corpuscles are the vehicles 

 of infection and the excitors of morbid processes. Presumably they 

 cause, when introduced into the vessels, a decomposition of the 

 blood, and thus generate by-products, which even in infinitesimal 

 quantity cause disturbance of the normal vital processes. Cohn 

 testifies that all the organisms yet demonstrated in contagious 



