162 BACTERIOLOGY. 



dehyde also forms combinations with certain aniline 

 colors viz., fuchsin and safranin the shades of which 

 are thereby changed or intensified. These are the only 

 colors, however, which are thus affected, and as they 

 are seldom used in dyeing, owing to their liability to 

 fade, this effect is of little practical significance. The 

 most delicate fabrics of silk, wool, cotton, fur, leather 

 etc., are unaffected in texture or color by formaldehyde. 

 Iron and steel are attacked, after long exposure, by the 

 gas, and more so by its solution; but copper, brass, 

 nickel, zinc, silver, and gilt work are not at all acted 

 upon. Formaldehyde unites with nitrogenous products 

 of decay fermentation or decomposition forming true 

 chemical compounds, which are odorless and sterile. It 

 is thus a true deodorizer in that it does not replace one 

 odor by another more powerful, but forms new chemical 

 compounds which are odorless. Formaldehyde has a 

 peculiar action upon albumin, which it transforms into 

 an insoluble and indecomposable substance. It ren- 

 ders gelatin insoluble in boiling water and most acids 

 and alkalies. It is from this property of combining 

 chemically with the albuminoids forming the protoplasm 

 of bacteria that formaldehyde is supposed to derive its 

 bactericidal powers. Formaldehyde is an excellent pre- 

 servative of organic products. It has been proposed to 

 make use of this action for the preservation of meat, 

 milk, and other food products; but, according to Trillat 

 and other investigators, formaldehyde renders these sub- 

 stances indigestible and unfit for food. It has been 

 successfully employed, however, as a preservative of 

 pathological and histological specimens. 



There are no exact experiments recorded of the 

 physiological action of formaldehyde on the human 



