CHAPTER XVII. 
THE BACILLUS MUCOSUS CAPSULATUS GROUP. 
Bacillus Mucosus Capsulatus Group. Bacillus Acidi Lactici. 
Bacillus Rhinoscleromatis. I Bacillus Lactis Aerogenes. 
Bacillus Ozsense. I Bacillus Aminophilus. 
The first member of these bacteria commonly known as the pneumo- 
bacilkis Group or the mucosus capsulatus group was isolated by 
Friedlander^ from pneumonic lungs. At that time he believed his 
"pneumonia micrococcus" was the causative agent of lobar pneumonia, 
and it was so regarded until Frankel- and Weichselbaum^ pointed out 
its comparative infrequency in lobar pneumonia, and differentiated it 
clearly from the pneumococcus, the true etiological organism of this 
disease. Weichselbaum also correctly interpreted its morphology and 
conferred upon it the name Bacillus pneumonise. Subsequent investi- 
gations by many observers have added several closely related bacteria 
to the group which at the present time comprises the following some- 
what imperfectly-differentiated types; B. mucosus capsulatus (Fried- 
lander's pneumobacillus), B. rhinoscleromatis,^ B. ozaenae,' B. lactis 
aerogenes,^ B. acidi lactici^ and B. aminophilus. 
The precise status of the group is still a matter of discussion and the 
work of Theobald Smith and his associates^ upon certain encapsulated, 
and mutable strains of B. coli has reawakened interest in the problem. 
For the present, however, the group may be considered as in good 
standing. 
Morphology.— The members of the mucosus capsulatus group are 
bacilli which vary in size and shape in the same culture from oval, 
almost coccoid elements, to distinctly elongated rods. The limits of 
size are comprised practically within the following dimensions: diam- 
eter, 0.5 to 1.2 microns, length, 0.6 to 3.5 microns. They occur 
typically singly or in pairs, less commonly united in short chains. 
Motility is not observed in cultures of any members of the group and 
they appear to be devoid of flagella. Spores have not been detected. 
A well-defined capsule, readily demonstrable by capsule stains, sur- 
rounds each organism if it is examined in tissues or secretions of the 
animal body, or in albuminous media. It tends to disappear during 
prolonged cultivation in the usual artificial laboratory media. Ordi- 
1 Virchow's Arch., 1882, 87, 319; Fortschr. d. Med., 1883, 1, 715. 
2 Ztschr. f. klin. Med., 1886, 10, 401. 
3 Wien. klin. Wchnschr., 1888, 1, 573; Centralbl. f. Bakteriol., 1889, 5, 33. 
* V. Frisch: Wien. med. Wchnschr., 1882, 32, 970. 
5 Abel: Ztschr. f. Hyg., 1896, 21, 89; Centralbl. f. Bakteriol.. 1893, 13, 161. 
8 Eecherich: Darmbakterien des Siiuglings, Stuttgart, 1886, p. 57. 
' Hueppe: Deutsch. med. Wchnschr., 1884, 10, 777. 
* .Jour. Exp. Med; 1927, 46, 133 et seq. 
