40 BACTERIOLOGY. 



for alkaloids, such as chloride of gold, double iodide of mercury 

 and potassium, picric acid, and tannin. Phospho-molybdic acid 

 precipitates them without exception. They are powerful reducing 

 agents. Ferro-cyanide of potassium is converted into ferri-cyanide in 

 their presence, and the addition of ferric chloride gives the Prussian 

 blue test. Selmi discovered this test, and Brouardel and Boutmy 

 regarded it as absolutely characteristic of ptomaines ; but this is 

 . not the case ; some vegetable alkaloids, for example, behave in the 

 same way. 



As examples of the non-oxygenous ptomaines there are : — 



Parvolin (O'H^'N') an oily base of an amber colour prepared 

 from putrid mackerel and horse-flesh. 



Uyd/rocollidin {&HP1S), from the same source. It is highly toxic, 

 being compared by Gautier to the venom of the cobra di capello. 



Collidin (O^Hi'N), from putrid gelatine and the pancreas of a 

 bullock, also highly toxic. 



JVetiridin (O'Hi^N^), from fish, flesh, and decaying cheese. 



Saprin (C^H^^N^), isomeric with neuridin. 



Cadaverin (O^Hi^N^), a third isomeride, from ordinary putrefac- 

 tion and herring brine. 



Putrescin (C*H^^]Sr^) from putrefaction. 



The oxygenous ptomaines are in some instances found also in 

 healthy tissues. They include the following : — 



Neurin (O^H^^NO), found in cadaveric putrefaction. 



Cholin (C-'^H^NO^), in bile. 



Musoarin (O^H'^NO^), in a poisonous mushroom, Agarieus mus- 

 carius, and in putrid fish. These are all highly poisonous. 



Gadinin{C'H}^'SiO^), in putrefying codfish. 



Mytilotoxin (C^Hi'NO^), in poisonous mussels. 



Poisonous alkaloids are of great importance in connection with 

 those cases of meat poisoning produced by sausages, hams, poultry, 

 and cheese. Tyrotoxicon is a poisonous alkaloid obtained from cheese. 



The toxic substances of most interest to the bacteriologist are 

 those isolated from pure ciiltivations of pathogenic bacteria, such as 

 typhotoxin, isolated by Brieger from cultivations of the bacillus of 

 typhoid fever, and tetanin, from cultivations of the tetanus baciUus • 

 and the poisons known as albumoses or tox-albumins, which are 

 allied to the albumose of snake poison. 



Pasteur, in 1885, suggested that in anti-rabic inoculations the 

 immunity resulted from the action of a, substance secreted by a 

 microbe, though the microbe has not as yet been discovei-ed in 

 rabies. Salmon produced immtinity from hog cholera by the injec- 



