Formaldehyde fixation.

The use of formaldehyde as a biological reagent occurred rather late in the history of histological methodology. The reason for this lay not in any lack of astuteness on the part of pathologists and histologists, but rather with the late development of formaldehyde manufacture by the chemical industry. While formaldehyde was discovered by Butlerov in 1859, practical aspects of the manufacture of this, the simplest aldehyde, only emerged in 1868 when Van Hoffman, as an academic exercise, developed a practical method for synthesis from methanol, and further established its properties. First production of formaldehyde as an industrial reagent occurred after the patent issued to Trillat in 1889, who in turn licensed several firms in France and Germany for manufacture (27). One such firm was Meister, Lucius and Brunig, located at Hoechst am Main, near Frankfurt am Main. While this firm, later to become one of the giants of chemical manufacturing under the name Hoechst, probably did not manufacture formaldehyde on any appreciable scale until 1891 (27), there was considerable interest in developing uses for formaldehyde. One likely possibility was in finding medical applications for aqueous solutions of formaldehyde. There had been reports from France that aqueous formaldehyde could be used as an antiseptic, either to treat or prevent wound infections. At that time, only a relatively few antiseptic agents were available and most of these were highly toxic and corrosive to tissues and instruments alike. The possibility that formaldehyde solutions might provide a "nontoxic sublimate" was a desirable goal that was not lost on Meister, Lucius and Brunig. In 1892 the firm approached a young physician in Frankfurt with the proposal that he test the antiseptic properties of formaldehyde. This young man, Ferdinand Blum, was a native of Frankfurt, born 3 October 1865. He attended the Universities of Kiel, Munich, Heidelburg, and graduated in medicine from Freiburg. Following graduation, and in the fashion of the time, he worked in several clinics, including the mental hospital at Schloss Marbach and the gynecologic clinic at Freiburg. On his return to Frankfurt he began a remarkable career, beginning with the project with Meister, Lucius and Brunig (14). His approach to this assignment was usual for the time. Formaldehyde was supplied by the manufacturer in a 40% aqueous solution, which is the concentration resulting from bubbling formaldehyde gas through water until no more will dissolve. Blum diluted the commercial solution for testing. The dilution he chose was a decimal one, or one part of commercial reagent diluted with nine parts of water to give a 4% weight/volume solution. He tested the bacteriocidal properties of this dilution against several bacterial species, including Bacillus anthracis, B. typhi', Staphylococcus aureus, and Proteus sp. The results of these experiments showed that formaldehyde was an effective but slow agent for killing bacteria (3). An incidental finding of this research was to have a far broader use and was reported by Blum in a second paper a few months later. In his second paper on formaldehyde, Blum reported that in the process of studying disinfection, he noticed that the skin of his fingers that had come in contact with the diluted solution became hardened, much as with alcohol, then one of the commonest methods for hardening tissues for histological processing. When he examined the tissues of an anthrax infected mouse preserved in formaldehyde, he found that the tissues had the same consistency as alcohol hardened or "fixed" tissues. When tissue samples were prepared for histology after formaldehyde treatment, excellent staining results were obtained using common staining methods of the time, such as hematoxylin and the analine dyes. The famous Frankfurt histologist, Wiegert, consented to examine some of Blum's preparations of various organs and found them entirely suitable for critical use. Better still, formaldehyde produced only marginal shrinkage and distortion of tissues, unlike alcohol fixed tissues (4,5). An account of formaldehyde would not be complete without some further information about Ferdinand Blum. After two initial papers about the use of formaldehyde, Blum was launched on a remarkable career in experimental medicine. By 1896 he was able to cite over 50 references to the use of formaldehyde by investigators in all areas of biology and medicine (6). At that time, Blum was appointed to the new Paul Ehrlich Institute where he started his life's work in endocrinology and general medicine. His work continued unabated through World War I, the economic chaos of Germany in the twenties, and the early years of National Socialism. In 1939, Blum, who had been friend and physician to most of the Jewish community of Frankfurt, including the Rothschilds and the Mertons, fled Germany at the age of 75 to begin a new career