168 BACTERIAL POISOXS. 



by either of the methods, he could obtain a substance which 

 gave alkaloidal reactions, and which he demonstrated to be 

 choline. His experiments led him to believe that choline 

 did not exist pre-formed in these fresh tissues, but that it 

 resulted from the action of the dilute acids upon lecithin. 

 It was found most abundantly in those tissues which are 

 rich in lecithin, such as the yolks of eggs, brain, liver, 

 and blood ; while only traces could be obtained from the 

 whites of eggs, lungs, and heart. The method of Dragen- 

 DOEFF was found to furnish much larger quantities of 

 choline than could be obtained by the Stas-Otto method. 



Coppola agrees with his countrymen, mentioned above, 

 in condemning the method of Dragendorff. 



Enough has been said to show that results obtained by 

 the Stas-Otto method are much more reliable than those 

 secured by the method of Dragendorff. However, the 

 former is not a perfect method, nor has a perfect one yet 

 been devised. The principal difficulties met with in the 

 Stas-Otto method are as follows : 



(1) In most instances the extraction of the base is very 

 incomplete. (2) The degree to which the putrefactive 

 alkaloid is removed by the solvent will depend very 

 largely upon the nature of the other substances present. 

 This fact in some cases aids and in others hinders the 

 labors of the investigator. Thus, several ptomaines, which 

 when pure are wholly insoluble in ether, may be removed, 

 in part at least, from organic mixtures by this solvent by 

 passing into the solution along with other substances, but 

 if the attempt is made to purify one of these bases by re- 

 peated solution and extraction with ether, the result is a 

 failure, because the more perfectly the alkaloid is freed 

 from impurities, the less soluble it is in ether. This criti- 

 cism, however, is equally applicable to the Dragendorff 

 method, and to all others in so far as extractions are made. 



However, we may state that whenever it is applicable 

 this' method is the best now employed. By it the sub- 

 stances are submitted to the least chemical manipulation, 

 and the results obtained are the most reliable. Many of 

 the more complex putrefactive products are so easily de- 



