444 MICROBIOLOGY 



Intracellular toxins. These are toxins more intimately 

 associated with the bacterial cell. Little is known of their 

 nature, although some of them are not so easily injured by 

 heat as others. In the case of all toxins the fatal dose for an 

 animal varies directly with the species, body weight, age, and 

 previous condition as to food, temperature, etc. In estimating 

 the minimum lethal dose of a toxin these factors must be care- 

 fully considered. 



Vegetable and animal poisons resembling toxins. Within 

 recent years it has been found that the bacterial poisons be- 

 long to a group of toxic bodies presenting very similar proper- 

 ties ; and which occur widely in the vegetable and animal king- 

 doms. Among plants the best known examples are the ricin 

 and abrin poisons, obtained by making water emulsions of the 

 seeds of the Ricinus communis and the Abrus precatorius 

 (jequirity) respectively. The chemical reactions of ricin and 

 abrin correspond to those of the bacterial toxins. They are 

 soluble in water ; they are precipitated by strong alcohol ; and 

 they are less easily dialyzed than the albumoses. They have 

 been called toxalbumins. Their toxicity is impaired by boil- 

 ing. They are among the most powerful poisons known, ricin 

 being the more fatal. 



It is also stated with certainty that the poisons of scor- 

 pions and of poisonous snakes belong to the same group. The 

 poisons derived from the latter are usually called venoms, and 

 a considerable number of such venoms derived from different 

 species have been studied. It may be stated that there is ob- 

 tainable from the natural secretions of the poison glands of- 

 certain snakes venoms which have all the reactions of the 

 poisonous bodies derived from bacteria. Like ricin and abrin, 

 the venoms are not so easily dialyzed as the bacterial toxins, 

 and therefore they have, also been classed as toxalbumins. 



Tissue response or specific products given off by the body 

 cells as a result of stimulation with protoplasmic alien sub- 

 stances. Perhaps the most striking reaction of the body 

 tissues when acted upon by toxins is the production of anti- 

 bodies or a substance that will neutralize the effect of the 



