Diagnosis from cells.

The methods used by Virchow which led to his work on cellular pathology are more akin to those of the cytologist than the morbid anatomist. The year 1858 is also notable for the first satisfactory staining of a histological section by Joseph von Gerlach (Fig. 1), as the result of a fortunate accident (Gerlach, 1858a and b). One evening, thanks to an oversight, he left cerebellum fixed in potassium bichromate in a very dilute solution of ammonia carmine. The following day the sections showed much better differentiation of nerve cells and fibres than had ever been seen before. Twenty-five years later Gierke wrote a history -of staining to celebrate Gerlach's discovery. Gierke believed that Gerlach was the first to stain a section, although so much good work had been done earlier that now it is not easy to say which advances actually came from Gerlach's discovery. Earlier work of great value included that of Corti, who in 1851 wrote " Reserches sur l'organe de l'ouie des mammiferes." In 1854 Hartig (1854, a, b, and c) found that the nucleus of a cell stains only after it is dead, and that the granules of chlorophil have an affinity for carmine, and in 1849 Goeppert and Cohn used carmine and madder to make cell contents more visible. Hill's (Fig. 2) remarkable work (1770) included the use of maceration, fixation (spirits of wine), mordants (alum, sugar of lead), metallic impregnation (quicklime and orpiment in succession to stain stems brown), and stains (cochineal and boiling green sealing wax). Finally the greatest credit must go to Anthony van Leeuwenhoek (1719), the discoverer of the microscope, who compared the muscles of a fat and a thin cow after staining with crocus (saffron) macerated in spirits of wine. He tells us that he prepared very thin sections so that they were quite transparent. This experiment was described in a letter to the Royal Society dated August 21, 1714, but was not published for five years. It is therefore more accurate to say that Gerlach was the first to popularize histological methods in morbid anatomy. Diagnostic cytology is the senior science. Virchow and his pupils used both cytology and histology, and a number of eminent pathologists, including Dudgeon and Ewing, continued this habit until recent times. The majority of pathologists, however, abandoned cytology and even denied it any place in diagnostic methods. So Durck (1904) wrote: