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BACTERIOLOGY. 



molecule. This can be understood from the following- 

 formulae! 



/ H 



N H 



Ammonia. 



/ H 



N H 

 X CH 3 



Methylamin. 



/ H 

 N-CH 3 



X CH 3 



Di-methylamin. 



N-CH 3 

 X CH 3 



Tri-methylamin. 



The amines possess a fish- or herring-like odor. Com- 

 pounds of this kind are present in herring-brine and are 

 frequently formed in the decomposition of protein matter. 

 Inasmuch as they are organic and basic in character they 

 belong to the group of ptomains. 



Acids. Products of this kind are very common. They 

 usually result from the oxidation of carbohydrates. Thus, 

 glucose is readily split up into acid products by a large 

 number of bacteria. One organism may convert it into 

 lactic acid, whereas another may produce butyric acid. 

 Hydrogen sulphide, an acid product, will, of course, be 

 formed only out of certain sulphur containing compounds, 

 such as the proteins. These compounds, moreover, may 

 give rise to various fatty acids. 



It must be understood that a given organism may pro- 

 duce acids and alkalis at the same time. The final reaction 

 in that case will depend upon which of these compounds is 

 present in excess. It not infrequently happens that an 

 alkaline medium turns acid and then, after a few days, 

 again becomes alkaline. 



The acid products of bacteria are very numerous. The 

 fatty acid series is usually represented by formic, acetic, 

 propionic and butyric acids. The higher fatty acids, such 

 as stearic and palmitic acids, will form in the decom- 

 position of proteins, or of fats. Lactic acid is very com- 

 mon. Oxalic and succinic acids may also be formed. 

 Carbonic acid and hydrogen sulphide are likewise to be 



