PREFACE TO P^«SsT EDITION. 

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Within the past ten ^ years much has been said and 

 written concerning the basic substances formed during the 

 putrefaction of organic matter, and those which are pro- 

 duced by tlie normal tissue-changes in the living organism. 

 Many investigators have given their wliole time and atten- 

 tion to the study of these substances, and important discov- 

 eries have been made and much light has been thrown upon 

 what have heretofore been considered problems in medical 

 science. To collect, arrange, and systematize the facts 

 concerning ptomaines and leucomaines has been our first 

 object. Although many short essays, some of them of 

 great value, have been written with the above-mentioned 

 object in view, the present work may be regarded as the 

 first attempt to make this collation embrace everything of 

 importance on this subject. In endeavoring to accomplish 

 this object we have met with many difficulties. The original 

 reports of the various investigators are scattered through 

 the pages of medical and scientific journals, transactions of 

 societies, monographs, government reports, etc. However, 

 with few exceptions we have been able to obtain the original 



