276 BACTERIOLOGICAL METHODS 



fungi or higher plants, possess the very characteristic property of 

 forming antibodies or antitoxins. Thus there is antivenin used in 

 the treatment of snake-bite, also antibodies used in the treatment 

 of hay fever, etc., which products are more fully described in works 

 on medical bacteriology. 



Frog Tests for the Presence of Alkaloids. — ^Lively small frogs 

 respond quite readily to the action of even high dilutions or very 

 minute quantities of vegetable alkaloids. It is suggested that 

 the food bacteriologists perform the following tests, which are 

 frequently desired as a check or corroboration of the findings of 

 the chemist and toxicologist. 



The material used for the frog injections is the evaporated 

 ether extract dissolved in a small amount of sterilized distilled 

 water. The injections are made hypodermically in the lymph sac 

 on the back of the frog. It is advised that the tests be made in 

 duplicate and repeated as often as may be required to attain ab- 

 solutely conclusive results. Each test should be checked by in- 

 jecting approximately minimal fatal doses of the pure alkaloid it- 

 self, obtained from some reliable house. This will make it pos- 

 sible to note the toxic symptoms produced by the pure alkaloid, and 

 compare with the symptoms produced by the suspected alkaloid in 

 the substance under consideration. These check tests are gener- 

 ally omitted by the analyst who has had extensive laboratory ex- 

 perience and who is therefore in a position to recognize the nature 

 of the poison (alkaloid) from the symptoms manifested by the 

 inoculated frog. In many instances the frog alkaloidal tests may 

 serve as checks upon the blood tests already described. 



In extracting the suspected substances it must be kept in mind 

 that alkaloids are very sparingly soluble in water, but when acidu- 

 lated (hydrochloric acid about i per cent.) water is used the acid 

 forms the salt (chloride) which is readily soluble in water. Alka- 

 loids are soluble in ether and in mixtures of ether and chloroform, 

 therefore these reagents should be used rather than the acidulated 

 water, especially since they are also antiseptic and the extractives 



