1 8 PASTORAL AND AGRICULTURAL BOTANY 



group. The narcotic action of many substances on the other hand is 

 associated with the presence of alkyl groups, especially ethyl groups. 

 The alkyl group is the active portion of the molecule in the alcohols, and 

 not the hydroxyl group. If halogen and especially chlorine replaces the 

 hydrogen atoms in a hydrocarbon, the narcotic action is greatly increased. 

 The presence of an ethyl group in a considerable number of compounds, 

 gives to the substance the power of connecting with the nervous system. 

 An excessively large dose of ethyl alcohol produces sleep, but a number 

 of compounds with ethyl groups have been discovered which have a hyp- 

 notic action in smaller doses. 



Alkaloids. The alkaloids are not widely distributed in the vegetable 

 kingdom. They are classified usually into five groups, as follows: (i) 

 Pyridin Alkaloids, such as coniin from Conium maculatum, nicotin 

 from Nicotina tabacum. (2) Pyrrolidin, Alkaloids. (3) Tropan Alkaloids, 

 such as atropin from Atropa Belladonna. (4) Quinolin Alkaloids, as 

 strychnin from Strychnos Nux-wmica. (5) Isoquinolin Alkaloids, as 

 morphin. Four elements carbon, hydrogen, nitrogen and oxygen enter 

 into the formation of the alkaloid. A few contain no oxygen. Most are 

 colorless crystalline solids, a few being liquid. Most are insoluble in 

 water, but dissolve in ether, alcohol, chloroform. They have a bitter taste 

 and have strong physiological, or toxic properties, even in small doses, 

 and a slight alteration in molecular structure often produces a decided 

 change in their physiological and toxic properties. For example, the 

 reduction of the nitrogenous ring generally produces a marked increase 

 in the toxicity and strength of the action of the poison and sometimes 

 alters its character. Pyridin is non t^xic and lowers blood pressure, but 

 piperidin is very toxic and raises blood pressure. The size and position 

 of the side chains attached to the ring have an important effect. Pyridin 

 can by reduction yield more active substance by the entrance of aliphatic 

 chains which is accompanied by the appearance of intoxicating action. 

 The toxic action of piperidin itself, which is not very strong, is increased 

 in a methyl piperidin and still more in a methyl piperidin and a-propyl- 

 piperidin (coniin). The toxicity of these substances is in the ratio of 

 1:2:4:8. 



Ptomaines. The bacteria and certain fleshy fungi have associated 

 with their activities a number of basic substances with simple constitution, 

 such as methylamine CH 3 NH 2 ; dimethylamine, (CH 3 ) 2 NH; trimethy- 

 lamine, (CH 3 ) 3 N; putrescin, NH 2 (CH 2 ) 4 NH 2 ; 'cadaverin, NH 2 (CH 2 ) 5 



