68 Biology of Micro-organisms 



the best known and most active acid producer. The butyric 

 fermentation generally due to Bacillus butyricus may also 

 be caused by other bacilli. (For an exact description of the 

 chemistry of the fermentations reference must be made to 

 special text-books.*) The lactic acid and butyric acid fer- 

 mentation, have the following equations: 



I. CH M Qu + H 2 Q = C H 12 2 + C,Hi,O fl 

 Lactose or milk sugar. Galactose. Dextrose. 



II. CoHiA = 2CzU,O 3 

 Galactose. Lactic acid. 



III. C 6 H, 2 6 = C 4 H 8 0^ + C0 2 + 2H 2 

 Galactose. Butyric acid. 



Putrefaction. Putrefaction is a chemic disintegration 

 of nitrogenous compounds resulting from the activity of 

 micro-organisms. The first step in the process seems to 

 be the transformation of the albumins into peptones, then 

 the splitting up of the peptones into gases, acids, bases, 

 and salts. Both fermentative and putrefactive processes 

 apparently take place through the agency of enzymes. 

 In the process the innocuous albumins are frequently changed 

 to toxalbumins, and sometimes to peculiar putrefactive al- 

 kaloids known as ptomains. 



Ptomains. Vaughan and Novy define a ptomain as " a 

 chemical compound, basic in character, formed by the action 

 of bacteria on organic matter." The chemistry of these 

 bodies is very complex, and for a satisfactory description 

 of them Vaughan and Novy's bookf is excellent. 



Ptomains probably play but a small part in pathologic 

 conditions. They are formed almost exclusively outside of 

 the living body, and only become a source of danger when 

 ingested with the food. It is supposed that cases of ice- 

 cream and cheese-poisoning are usually due to tyrotoxicon, 

 a ptomain produced by the putrefaction of the protein sub- 

 stances of the milk before it is frozen into ice-cream or 

 made into cheese. The safeguard is to freeze the milk only 



*See "Enzymes and Their Applications," by Jean Effront, trans- 

 lated by S. C. Prescott, New York, 1902; "Micro-organisms and Fer- 

 mentation," by Alfred Jorgensen, translated by A. K. Miller and 

 A. E. Lennholm, London, 1900; and the many writings of Christian 

 Hansen. 



f "Ptomaines and Leucomaines," 1888; "Cellular Toxins," 1902. 



