Since the first description by Friedlaender in 1883, and by Weichselbaum three years later, of an organism which was first called a coccus (pneumococcus of Friedlaender) and later regarded as a bacillus, occurring in acute fibrinous or croupous pneumonia, this bacillus has been found by many observers in various inflammatory processes in the lungs and other organs.
As specific characteristics of this organism were pointed out, its raised mucus-like growth on agar and blood serum, its nail-shaped growth on gelatin, its yellowish-gray growth with gas formation on potato, its failure to coagulate milk, absence of indol reaction, and decolorization by Gram's method of staining; it was generally found to be constantly pathogenic for mice, variably so for guinea pigs (fatal in about one-half of the cases), rabbits and pigeons, and finally its polymorphism and capsule formation were regarded as quite specific. From time to time bacilli differing in some respects
THE BACILLUS MUCOSUS CAPSULATUS (BACILLUS OF FRIEDLAENDER).. JAMA. 1898;XXX(17):990-991. doi:10.1001/jama.1898.02440690050007