The preparation and use of bacteriophages against the colon bacilli present special problems. The difficulties appear to be due in part to the numerous varieties and strains of bacteria included within this group and in part to the long continued association between the colon bacilli and various lytic agents of the bacteriophage group in the intestines of man and other vertebrates. A great variety of possibilities is thus presented.
Furthermore, the location of the pathologic condition in the patient may introduce additional complicating circumstances. The infectious process may be located on a surface in contact with abundant other bacteria, as in intestinal ulcer, or in contact with a more or less irritating or toxic liquid, such as the urine, in a wound or in the interior of the blood vessels. The special conditions present at the site of the infection may require careful consideration and sometimes modification in order to