Chemical Agents. 51 



poisonous, the amorphous red form being harmless even in large 

 quantities. A number of substances which are insoluble in water, 

 and which have practically no effect when brought in contact with 

 the skin or when introduced subcutaneously, are changed by the 

 hydrochloric acid of the stomach so as to become serious poisons ; 

 for example, carbonate of barium is changed in the stomach 

 into the soluble chloride of barium. On the other hand, there 

 are substances which are apparently energetic poisons when in- 

 troduced into the blood, but which are inert in the stomach be- 

 cause they are completely neutralized by the albuminates of the 

 gastric juice (Samuel). 



Many poisons belong to the mi)ieral kingdom or are artifi- 

 cially made from minerals, as arsenic, mercury, iodine, bromine, 

 chlorine, lead, copper and others, and the various compounds of 

 these substances (oxides, sulphides, chlorates, chlorides, etc.). 

 The organic compounds, as alcohol, chloroform, hydrocyanic acid, 

 cyanide of potassium, carbolic acid and picric acid, especially 

 [include many poisons]. 



The vegetable kingdom (Samuel) affords many examples of 

 poisons. There are whole families of plants w'hose genera and 

 species possess some poisonous principle common to them all. In 

 many plants certain parts may contain a poisonous substance, 

 while the rest may be quite free from it and edible (as is well 

 known in case of potato plants, solanum tuberosum, w'hose leaves, 

 blossoms, seed and immature fruit contain the poisonous solanin, 

 while the tubers are quite free from it). A number of plants are 

 innocuous, slightly or seriously poisonous, depending upon ques- 

 tions of climate, location, character of the soil and cultivation ; 

 the almond tree, for example, bears either sweet or bitter al- 

 monds, according to the location. The most pow-erful poisons 

 contained in the higher plants are the vegetable alkaloids (mor- 

 phine, atropine, colchicine, digitaline, etc.). In case of the 

 lower plants also, especially the bacteria, there are products, some 

 of which are marvelously toxic, fatal to large animals in the 

 most minute and scarcely appreciable amounts ; these substances, 

 analogous to the alkaloids and enzymes, or of albuminous nature, 

 are embraced by the terms toxines, to.ralbuuiens, foxenaymes. 

 (See also chapter on bacteria.) 



Among animals there are a number known to be able to 

 elaborate poisonous secretions within special glands, especially 

 the venomous snakes {viper a berus, the common adder of Ger- 



