6 Parasitic Bacteria and their Relation to Saprophytes. [Jan. 
ing the animal body. In fact, it cannot complete this cycle 
within the body, for that most important stage—spore formation 
—only takes place on exposure to the air, so that bacilli within 
the dead body, if immediately buried, do not form spores. These 
facts illustrate clearly the preponderance of a saprophytic life in 
this very virulent organism. 
To indicate graphically the probable phylogenesis of parasitic 
bacteria, Hüppe has constructed the following table, according to 
De Bary: 
True Saprophytes. ——————_—_______, 
f 
I. Ferment bacteria. 2. Pigment bacteria. 3- Parasitic bacteria. 
————_—Aerobiotic. 
| Facultative parasites. 
—— 
Agents of | 
oxidization fermentations. Facultative anaerobiotic. Facultative saprophytes. 
Obligatory eae Oleo ce. 
The term facultative parasites signifies that the bacteria in- 
cluded in the class are capable of living as parasites or of pass- 
ing through certain stages of their development as parasites. 
Facultative saprophytes are such parasites which may live 
as saprophytes either during the whole or a part of their life- 
cycle. $ 
If for a moment we look more carefully at the parasitic life 
of bacteria, a number of interesting facts and problems appear. 
First of all each microbe produces definitely characterized symp- 
toms and lesions which are grouped together as a specific disease, 
According to the abode which the microbes choose in the animal 
body, these symptoms and lesions will vary within wide limits. 
Some species multiply within the capillary system of the various 
organs, some are confined to the lymphatics, while others pro- 
duce suppuration in the connective tissue by attracting an army 
of leucocytes to oppose them. A few are constantly found with- 
in leucocytes themselves. Some bacterial diseases are limited to 
Special organs or tissues. It may be the lungs or the spleen, the 
skin or the mucous membrane of the intestine which becomes 
the seat of attack, and to which the disease remains restricted. 
In the various situations minor modifications in disposition and 
‘grouping give rise to diseases of quite different character. 
Bacteria growing in dense plugs in the capillaries produce in- 
