FOREWORD IX 



Macallum's reaction for potassium, and the popular methods for 

 the detection of phosphatases. In all of these, the possibility for the 

 adsorption of molybdic, cobalt, or lead ions, respectively, independ- 

 ent of the reactions supposed to occur, should be entertained. 



Negative results should not be accepted; the limitations imposed 

 by the microscope as to the thickness of preparations both from the 

 standpoint of transparency and of dispersion of light make any 

 negative conclusions inadmissible. 



It may be inferred from the preceding remarks that this writer 

 views microchemical methods of this category with suspicion. This 

 is not the case. He simply wishes to insist that the worker scrutinize 

 critically every phase of his technique and consider seriously what 

 the value of the method may be for recognition, quantitation, and 

 localization, respectively. 



The second, third, and fourth parts of the volume are devoted to 

 the methods for accurate physical and chemical microanalysis as 

 applied to biological problems, and to the newer methods for the 

 mechanical separation of the morphological constituents of proto- 

 plasm. This writer has already indicated above his belief that in 

 these methods rests our chief hope of progress in the solution of the 

 mystery of life. 



The road to this goal is a long and laborious one. It is the writer's 

 hope and belief that travelers along this difficult highway will find 

 their burdens lightened by the collection into one volume of so many 

 useful methods of investigation. 



R. R. Bensley 



