66 



THE AMEEICAN MONTHLY 



[April, 



and likewise omit to cite authox-ities, 

 whereby the student might be enabled 

 to search for himself. The metallic 

 impregnation of tissues I have also 

 included, because the object of this 

 operation is the same as staining, to 

 wit, the differentiation of structure, 

 and also because a real coloration 

 sometimes results. 



A stranger entering a histological 

 laboratoi-y must be forcibly impressed 

 by the prominence given to staining. 

 Neither the microscope nor the mi- 

 crotome with its menacing knife is so 

 striking to the observer. The clear 

 light everywhere falls upon all the 

 hues of the rainbow. Cabinets full 

 of glowing colors, and tables covered 

 with brilliant stainings, are unex- 

 pected revelations. It is true the 

 earnest worker must often bewail 

 and condemn the tedious methods of 

 modern research, but he cannot do 

 without staining for we owe to it ex- 

 traordinary results in our investiga- 

 tion of animal tissues ; in fact, with- 

 out it our most important discoveries 

 in pathology and histology would be 

 impossible. It is true we are much 

 in the dark as to the exact natui-e of 

 staining. The chemical reactions in- 

 volved are not yet so clear but that ex- 

 perience is our best teacher, and we 

 must not confide too much in general- 

 izations respecting our methods. 



Nowhere is so much staining done 

 in microscopy as in Germany. The 

 methods in use elsewhere have mostly 

 been carried hither by Germans, or 

 by students educated in Germany. 

 In foreign works on microscopy, for 

 example, in Beale's ' How to work 

 with the Microscope,' manipulation 

 is treated with exhaustive particular- 

 ity unknown in German books, but 

 methods of staining occupy little 

 space. All important discoveries in 

 this direction have been made by Ger- 

 mans. Even the celebrated French 

 histologist, Ranvier, a master in mani- 

 pulation, is obliged to content him- 

 self with improving our methods. 



Gerlach is to be regarded as the 

 founder of this art. His discovery of 



the staining power of carmine, and 

 his recommendation of this dye, ex- 

 cited histologists to use it and to ex- 

 periment further. It is true, colored 

 injections and hardenmg fluids that 

 sometimes stained to some extent had 

 been previously used ; and if car- 

 mine-gelatin accidentally retained 

 an excess of ammonia when used as 

 an injecting fluid, the consequent 

 tinging of the tissues adjacent to the 

 vessels by the dissolved carmine could 

 hardly fail to be noticed, and thus sug- 

 gest staining in mass. Many inde- 

 pendent attempts were made to use 

 carmine. The botanists Goppert 

 and Cohn appear to have been the 

 first. {Botan. Zeitung^ 1843, No. 

 37.) They added a carmine so- 

 lution to the cell-contents of Nitella 

 Jlexilis to better study rotation and 

 determine if the chlorophyll masses 

 had cilia, and they remarked that 

 these masses were more deeply dyed 

 than the surrounding fluid. Welcker, 

 in 1S58, used carmine for studying 

 the cell-nucleus of muscle-fibres. In 

 England, Lord S. G. Osborne grew 

 plants in carmine solution. He like- 

 wise observed the nucleus grew dai'ker 

 than the other elements. More im- 

 portant were the efforts of Hartig for 

 a new method of investigation by 

 staining plant tissues with carmine 

 and other dyes. His results were 

 published at the time Gerlach first 

 turned his attention to carmine as a 

 stain. In connection with Hartig's 

 work that of the apothecary Maschke 

 should be mentioned, published in 

 1859. Hartig's researches went fur- 

 ther than even Gerlach. He showed 

 the tissue must be dead, in order to 

 take the dye, and he observed the 

 same results in plants that Gerlach 

 found in animal tissues. Among the 

 substances used by him were the juice 

 of Phytolacca decandra^ litmus, 

 black ink, cuprous sulphate, gam- 

 boge, and cinnabar. For a time 

 these experiments were fruitless, and 

 so it has come about that Gerlach has 

 received credit as the real discoverer 

 of staining. 



