Xll INTRODUCTION. 



under the microscope, that we designate by the 

 word micro-chemistry. 



I have endeavored to successively make the 

 reader acquainted with the most valuable reagents 

 used in micro-chemistry, i. e. with those sub- 

 stances whose action on the bodies to be studied 

 allows their chemical composition and nature, 

 and sometimes their physical structure, to be 

 recognized. In the first section I have consid- 

 ered the chemicals used in the laboratory ; in the 

 second, the vegetable substances to be tested for 

 and the reactions by which they are known. 



The correctness of the statements which follow 

 rests in part on the long experience of my re- 

 spected teacher, Dr. Warming, and in part on 

 my own. I have also been able to profit by the 

 practice and teaching of Professor Han stein, of 

 Bonn, made known to me by Dr. Warming. 

 Finally, the scattered experiments and methods, 

 recorded in a large and scattered literature, have 

 been used so far as possible, far be it from me, 

 however, to suppose that I have exhausted the 

 literature ; nor have I tried to take up all of the 

 chemicals that have been used, my endeavor being 

 to collect only such as are most useful. 



At the close of the first section I have intro- 

 duced a short chapter on media for the preserva- 

 tion of permanent preparations ; to which are 

 added a few words on the cements used in 

 mounting. 



