SUGAR IN THE NUTRIENT MEDIUM. 157 



Such experiments were formerly made chiefly by 

 Fitz, and recently have been performed with pure 

 cultures and interesting results by P. Frankland. A 

 couple of illustrations will suffice. Pasteur found 

 that anaerobic bacteria convert lactate of lime into 

 butyrate of lime. 



2(CH 3 - CHOH - COO) 2 Ca = CO 3 Ca -f 3 CO 2 -f 4 H a + 

 Lactate of lime. (CH 3 - CH 2 -CH 2 - COO)Ca 



Butyrate of lime. 



According to P. Frankland the bacillus ethaceticus 

 Fitz converts glycerate of lime (CH 2 OH-CHOH- 

 COO) 2 Ca into ethyl alcohol, acetic acid, carbonic 

 acid, and hydrogen. 



III. THE PATHOGENIC EFFECTS OF BACTERIA. 



(Pathogenesis, Predisposition, Resistance, Im- 

 munity.) 



Whenever we are able to recognize the nature of the 

 pathogenic action of bacteria, they are found to act 

 by means of the chemical substances which they form 

 in the animal body or which are formed from them. 

 But hitherto we have learned to comprehend only the 

 action of those bacteria which produce toxic sub- 

 stances in cultures, and by means of which we can 

 reproduce the characteristic symptomatology in a 

 more or less accurate manner. 



The bacteria of this category include particularly 

 the bacillus tetani, bacillus diphtheriae, streptococcus 

 pyogenes, micrococcus pyogenes, vibrio cholerse, etc. 

 On page 134 we have given a brief sketch of our 

 chemical knowledge of these toxic substances. 



