The History of Staining the Development of Cytological Staining

Perhaps no other period has contributed more to our knowledge of the cell than the period 1875-1895. During these years most fundamental cytological phenomena were seen and described. Mitosis, maturation and fertilization, the great cornerstones of cytology, were firmly laid by the remarkable researches of Flemming, Strasburger, Van Beneden, Oscar and Richard Hertwig, Boveri and many others. Upon these researches experimental cytology developed and the significance of the morphological phenomena to inheritance and development was pointed out by such masters as W. Roux, Weismann, O. Hertwig, Boveri and E. B. Wilson.     

The History of Staining the Development of Cytological Staining

Perhaps no other period has contributed more to our knowledge of the cell than the period 1875-1895. During these years most fundamental cytological phenomena were seen and described. Mitosis, maturation and fertilization, the great cornerstones of cytology, were firmly laid by the remarkable researches of Flemming, Strasburger, Van Beneden, Oscar and Richard Hertwig, Boveri and many others. Upon these researches experimental cytology developed and the significance of the morphological phenomena to inheritance and development was pointed out by such masters as W. Roux, Weismann, O. Hertwig, Boveri and E. B. Wilson.     

The History of Staining the Development of Bacteriological Staining Methods

The staining of bacteria is naturally of later origin than the use of dyes in histological work, as the systematic study of bacteria did not begin until after 1870. The use of dyes in this study followed very promptly after that date, however.     

The Negative Staining of Bacteria

The author does not propose new methods but calls attention to the value of Burri's India ink technic and Fischer's use of nigrosin for the negative staining of bacteria. The latter is particularly useful. The technic is as follows: Boil 10 g. nigrosin in 100 cc. water about 30 minutes. Filter several times thru the same filter paper, adding 10 drops of formalin before the last filtration as a preservative. Place a small loopful of this solution on a clean slide and add the bacteria with a needle or loop. After mixing spread the mixture a little irregularly on the slide and dry either at room temperature or slowly over a low flame. The preparation may be examined in oil immersion without the use of a cover slip.     

The Selective Staining of Mitochondria

A critical analysis of extant selective mitochondrial stains has elucidated certain empirical criteria for the adoption of dyes for trial. These criteria include a specific triphenylmethane structure for the dye, with sulfonation and the use of aniline and heat as adjuvants. By the application of these characteristics the dyes fast green FGF and light green SF yellowish were chosen for study and proved to be highly selective mitochondrial stains. They are applicable to both tissue slices and homogenate studies and permit examination of the internal structure of mitochondria.     

The Germicidal Effect of Staining Solutions

Gentian violet, crystal violet and carbol fuchsin applied to cover slip preparations for one minute will destroy the majority of non-spore-forming bacteria and yeasts, tho they can not be relied upon to do this consistently and in all cases.

The Gram staining procedure is more effective and non-spore-formers were never found to survive this process.

Methylene blue stains exert very little if any germicidal power and most organisms survived them readily. India ink was totally ineffective.

Several species of yeasts and yeast-like molds were killed in every instance by the Gram stain, gentian violet, crystal violet and carbol fuchsin, but survived both Loeffler's methylene blue and a plain aqueous solution of methylene blue.     

The Physical Chemistry of Silver Staining

It has been shown that silver deposition plays a part in the silver staining process. From this it has been concluded that the rate of reduction of silver within and on histological structures is an important factor.

Some factors controlling the rate of reduction, such as the adsorption of silver hydroxide and ammonia, the affinity of silver for proteins, and the protective power of the gel structures have been pointed out.

Some simple applications of the ideas to silver staining have been given and two technics described, one making use of piperidine instead of ammonia, the other carrying out the reduction in the presence of the silver solution to facilitate deposition.     

The History of Staining Cochineal Dyes

Of the dyes used in early histological work, none was so highly prized as carmin. Even today biologists would be loath to part with it. It is still valuable to the histologist and embryologist as a bulk stain of great permanency, and for the preparation of in toto mounts. To the cytologist, also, it is invaluable as a medium for the rapid staining and examination of chromosomes in fresh material. Its permanence has always been a great advantage. To the early histologists, however, it was the dye, par excellence.     

The History of Staining Logwood Dyes

Except for the cochineal derivatives, logwood extract was the first of the important modern stains to be employed in histology. Certain other natural dyes, such as madder and indigo, had been used earlier, but they are of little significance in discussing the history of staining, because none of them nor even alizarin, the derivative of madder, are of any appreciable significance in these days of synthetic dyes. Hematoxylin, on the other hand, still continues a very important stain, and it has played an interesting part in the history of staining.     

The Germicidal Effect of Staining Solutions

Gentian violet, crystal violet and carbol fuchsin applied to cover slip preparations for one minute will destroy the majority of non-spore-forming bacteria and yeasts, tho they can not be relied upon to do this consistently and in all cases.

The Gram staining procedure is more effective and non-spore-formers were never found to survive this process.

Methylene blue stains exert very little if any germicidal power and most organisms survived them readily. India ink was totally ineffective.

Several species of yeasts and yeast-like molds were killed in every instance by the Gram stain, gentian violet, crystal violet and carbol fuchsin, but survived both Loeffler's methylene blue and a plain aqueous solution of methylene blue.     

The History of Staining Cochineal Dyes

Of the dyes used in early histological work, none was so highly prized as carmin. Even today biologists would be loath to part with it. It is still valuable to the histologist and embryologist as a bulk stain of great permanency, and for the preparation of in toto mounts. To the cytologist, also, it is invaluable as a medium for the rapid staining and examination of chromosomes in fresh material. Its permanence has always been a great advantage. To the early histologists, however, it was the dye, par excellence.     

The Surface Staining of Embedded Tissues

The staining procedure is based on the theory that the freshly cut surface of embedded material will absorb stain only in the exposed tissue elements, provided that the embedding compound itself will not absorb the staining fluid. Concentrated stains are used for short intervals to insure minimum penetration. For paraffin embedded materials: (1) Cut block, preferably on microtome, to the desired tissue surface. (2) Rinse in absolute alcohol. (3) Float face down in stain. (Ripe, concentrated alum hematoxylin—Galigher's formula recommended—will stain in 10 to IS minutes. Heidenhain's iron hematoxylin works exceptionally well in some cases.) Mordant 20% alum 5 to 10 minutes, briefly rinse, and stain comparable 5 to 10 minutes in 1 to 1.5% hematoxylin. (4) Allow to become blue in tap water (for hematoxylin stains). (5) Counter-stain if desired. (6) Dehydrate in absolute alcohol for not more than 10 minutes. (7) Dry for 15 to 20 minutes. (8) Trim block to 2-3 mm. and mount between two cover glasses by use of microflame. Attach mount to slide with balsam. For celloidin embedded materials: (1) Dehydrate block with 90% alcohol, phenol-toluene, finally pure toluene. (2) Rinse cut surface with 90% alcohol, then apply stain. (3) Wash, after hematoxylin stains, counterstain if desired. (4) Dehydrate surface, 90% alcohol, phenol toluene, pure toluene, and mount in medium dissolved in toluene.

Possible applications of surface staining technic are suggested and illustrated.     

The History of Staining Logwood Dyes

Except for the cochineal derivatives, logwood extract was the first of the important modern stains to be employed in histology. Certain other natural dyes, such as madder and indigo, had been used earlier, but they are of little significance in discussing the history of staining, because none of them nor even alizarin, the derivative of madder, are of any appreciable significance in these days of synthetic dyes. Hematoxylin, on the other hand, still continues a very important stain, and it has played an interesting part in the history of staining.     

The Weigert-Pal Technic for Staining Myelin

The writer gives a schedule for carrying out the Weigert-Pal technic by which three difficulties of the original technic are overcome: the tendency of the sections to become brittle; the difficulty of observing the extent of the reaction occurring in the permanganate solution; and the slowness with which the reaction takes place. By the method proposed as many as 300 sections may be stained and differentiated in the time it formerly took to handle 50.     

The Weigert-Pal Technic for Staining Myelin

The writer gives a schedule for carrying out the Weigert-Pal technic by which three difficulties of the original technic are overcome: the tendency of the sections to become brittle; the difficulty of observing the extent of the reaction occurring in the permanganate solution; and the slowness with which the reaction takes place. By the method proposed as many as 300 sections may be stained and differentiated in the time it formerly took to handle 50.