GENERAL CONSIDERATION OF DISEASE. 61 



Other bacteria produce a variety of pigmentation in food 

 substances. These pigments are variable in composition and 

 solubility. Generally speaking the bacterial pigments are not 

 injurious when consumed. Practically all pigment producing 

 bacteria are aerobic. 



The principal action of most bacteria is the result of the 

 activity of ferments or enzyms produced by the bacterial pro- 

 toplasm. Some of these bacterial ferments may produce their 

 specific activity while inside the bacterial body, others 

 bring about specific changes after being secreted and eliminated 

 from the bacterial body. The end products resulting from 

 the activity of bacterial enzyms or ferments are variable and 

 depend upon the specific enzym or ferment also on the comp ;- 

 sition of the substances acted upnn. Acids (jr alkalies represent 

 the end products of many of the bacterial decompositions. 

 Carbohydrates are usually converted ultimately into an acid, 

 carbon dioxide and water. Protein substances may be con- 

 verted into carbon dioxide, water and ammonia by the activitv 

 of Bacillus pyocvaneus. 



Putrefaction is a bacterial decomposition of nitrogenous 

 substances and occurs in the absence of air. The end products 

 of putrefaction are extremely ^-ariable ; liTi'drogen, carbon 

 dioxide, nitrogen, h}-drogen sulphid, and ammonia, are some 

 of the common gases that escape from a putrefving carcass ; 

 amido compounds, pepton, skatol and indol represent aromatic 

 compounds ; ptomains probably represent one of the most im- 

 portant putrefactive products. Ptomains are basic chemic 

 substances produced bv decomposition of nitrogenous ci im- 

 pounds. Thev are usually formed outside the body, although 

 they ma-\' be formed by putrefaction of the contents of the 

 intestine. Ptomain poisoning is usually the result of consump- 

 tion of foods contaminated \\'ith ptomains although it ma\' 

 result from the absorption of ptomains formed within the in- 

 testine. Sufficient ptomains may also be absorbed fmm 

 necrotic tissue to produce injurious efTects. 



The chemic substances produced by pathogenic bacteria are 

 probably of more importance than any other bacterial com- 

 pounds. Although thev have been extensively studied the com- 

 position of most of these compounds is still unknown. Three 

 groups of pathogenic bacterial products deserve mention .they 

 are (1) bacterial toxins, (3) endotoxins and (3) bacterial pro- 

 teids, 



1. P)acterial toxins are soluble, synthetical, poisonous, 

 chemic substances elaborated by the bacterial protoplasm and 



