General Remarks on Staining 71 



Delafield's haematoxylin in staining a vascular bundle, it will not 

 do to make the safranin just right and then apply the haematoxylin, 

 for the acid which must be used to differentiate the haematoxylin 

 and to avoid precipitates will also reduce the safranin, and the red 

 will be too weak. You must overstain in safranin so that the re- 

 duction will finally leave it just right. The same hint will apply if 

 safranin is to be followed by anilin blue, since here, also, acid must be 

 used; but if light green is to follow the safranin, no acid is necessary 

 and the safranin may be made about right before the second stain is 

 added. These hints are only samples: the student must observe the 

 behavior of the various stains when used singly and when used in 

 various combinations. 



Permanent preparations are an absolute necessity for the greater 

 part of most advanced work, but let us not imagine that we cannot 

 examine anything until we have made a permanent mount. It 

 would be impossible to make a permanent mount of the rotation of 

 protoplasm. It is better for many purposes to look at motile spores 

 while they are moving. Use Spirogyra while it is fresh and green, 

 and use permanent preparations only to bring out nuclei and other 

 details which are not so easily seen in living material. Examples 

 might be multiplied. 



