208 PROCEEDINGS OF SOCIETIES. 



of Appert, Sclivvaun, Schrdder, Duscli, Pasteur, and Tyndall, 

 appears to be contradicted by the very noteworthy investigations 

 of Burdon Sanderson, lately published in his ' Second Report of 

 Researches concerning the intimate Pathology of Contagion.' 

 According to these researches the germs of fungi do come to 

 putrescible substances from the air, but not the germs of bacteria. 

 Infection with bacteria is effected solely by contact with dirty sur- 

 faces (skin, instruments, or vessels), but especially by means of 

 water, which always, even when freshly distilled, contains bacteria 

 germs. Even saliva, urea, blood, pus, milk, egg albumen, may 

 become mouldy, but do not putrefy when exposed to the air, if they 

 are at the same time protected from contact with water containing 

 bacteria, or surfaces of the same kind. 



Cohn's researches have, indeed, only partially confirmed these 

 statements, but still chemical solutions exposed to the air were, as 

 Sanderson has shown, as a rule protected from putrefaction, but 

 not from mould. The convection through the air of bacteria 

 germs (the volatilization of which Cohn has directly demonstrated) 

 does at all events take place with ditRculty, — presumably because 

 the air is not sufficiently loaded with bacteria, — while infection 

 with water instantaneously causes putrefaction to begin. 



3. The nutrition of bacteria at the expense of the putrefying 

 albuminous substances is generally conceived of as if the bacteria 

 obtained the nitrogenous contents of their cells (protoplasma) imme- 

 diately from these substances. This view is, however, incorrect. 



While all animals do in reality form their nitrogenous tissues 

 out of the albuminous substances which they receive ready formed 

 with their food, bacteria, and presumably all fungi, agree with the 

 green plants in assimihiting the nitrogen of their protoplasma in 

 the form of ammonia or nitric acid. Bacteria, however, and fungi in 

 general, are on the other hand distinguished from the green plants 

 by absorbing the carbon which is a constituent of their cells, not 

 from carbonic acid, but from other more easily decomposed carbon 

 compounds, especially from carbohydrates, Pasteur had previously 

 found that yeast fungi go through their normal development in a 

 fluid containing ten parts crj'^stallized sugar candy, and one part of 

 ammonium tartrate in 100 parts of distilled water, and Sanderson 

 showed that Pasteur's fluid is also a suitable nutritive medium for 

 bacteria. The result of Cohn's researches is to prove that sugar is 

 not necessary for bacteria ; they develop and multiply in a perfectly 

 normal manner in any fluid which contains, beside ammonia or 

 nitric acid, a non-nitrogenous carbonaceous body. If a drop of fluid 

 containing bacteria be added to a one per cent, solution of am- 

 monium tartrate, the fluid remains clear for three days, and then if 

 maintained at a temperature of 30°, becomes turbid and gradually 

 milky, while thick bacterium mucus accumulates on the surface, till 

 after some weeks the fluid becomes clear again and deposits an 

 abundant precipitate of bacteria. Almost the same thing is 

 observed with solutions of ammonium succinate, potassium tartrate 



