CHAPTER I 



HISTORY OF STAINING 



CONSIDERING how dependent microscopists are today upon 

 the use of stains, it is hard to reahze that much important 

 work had been done with the microscope before the use of 

 stains was attempted. Altho natural dyes such as carmin and 

 indigo were well known in the early days of the microscope, their 

 use in staining microscopic preparations does not seem to have been 

 mentioned until about 1850; and anilin dyes were not put on the 

 market until 1856. Yet anyone who has studied the history of 

 biology must realize that many discoveries had been made with 

 the microscope before this period. 



It is safe to say, nevertheless, that the use of stains revolutionized 

 microscopic technic. The early microscopists were able to make 

 much progress without stains because of their painstaking dili- 

 gence. The work without stains must have been extremely diflScult, 

 and it is hard on reading some of the old publications to believe 

 that some of the minute structures described were actually seen. 

 Few users of the microscope today would be likely to have either 

 the patience or the eyesight to do the work described in those early 

 days. The fact that the microscope is now being used successfully 

 in the hands of so many students who would not think of comparing 

 themselves with the pioneers in microscopy is due to the use of 

 stains more than to any other factor — altho of course no one can 

 deny that modern improvements in the microscope have also 

 played a part of great importance. 



The first use of a dye in microscopic work seems to have been by 

 Ehrenberg (1838)*, who did not intentionally stain his specimens, 

 but devised the scheme of grindmg indigo and carmin into a very 

 fine powder and feeding them to the microorganisms he was study- 

 ing. His idea in doing this was that the organisms would consume 

 the dye bodily and that their digestive system could be traced by 

 observing what portions of the body became colored. Ehrenberg 

 found by this method that the organisms in question showed cer- 

 tain zones or bands of color; and assuming that each of these 

 colored spots was a stomach, he named the group of organisms 

 "Polygastrica." Inasmuch as the group included bacteria and 

 protozoa, the name was somewhat of a misnomer. It is interesting, 

 however, to realize that Ehrenberg's technic is still used to demon- 

 strate the ability of protozoa to engulf food particles. 



The early history of staining from this time on is given in a very 

 interesting manner by Gierke (1884-5) and by Mann (1902), one 



*For references cited see Bibliography pp. 138 to 145. 



