Tuberculous foci are induced in 36 guinea pigs devided into a sensitized group and a nonsensitized group, by intrabronchial injection of human tubercle bacilli, H(37)Rv strain. Of the group given nonchemotherapy 13 foci proved to be aid fast bacillus positive by Z.-N. test are taken as the control. Of the group receiving chemotherapy of SM, PAS, or INH singly, 13 foci proved to be bacillus positive are selected. With smear specimens prepared from the contents of these foci in the two groups and by means of Kuroda test, A.-F.-G. test and Z.-H. test concurrently, the authors studied morphological changes of tubercle bacilli in the focus as well as differences in the shape and stainability of bacilli due to the kinds of antituberculous agents; and obtained the following results.
1. In the caseous foci that received no chemotherapy mainly intermediate bacilli are found, and along with softening and subsequent cavitation long bacilli and acid fast type of bacilli by A.-F.-G. test tent to increase. And with inspissation there appear an increasing number of short bacilli as well as more deformed bacilli. On the other hand, bacilli in the case receiving chemotherapy gradually lose their acid resistance and at the same time they become fibrous, showing an increasing number of. short bacilli and more marked deformation. 2. Examining differences in the shape and stainability of bacilli due to different kinds of antituberculous agents employed, in the case given SM the change in the length is not so marked, but the deformation of bacilli as well as the fall in the acid resistance are most marked when compared with the case of PAS- and INH-administrations. Change in the length of bacilli in the case of PAS administration is likewise not so marked, but the effect exerted on the acid resistance is least. In the case of INH administration the lengthening of bacilli is most striking. 3. There can be found no marked differences in the shape and stainability of bacilli between the sensitized group and the non-senstitized group. 4. Even in the group given no chemotherapy bacilli of stain (positive) and culture (-) can be recognized, and although those of stain (positive) and culture (positive) are increased by chemotherapy, no other specific deformation can be observed. The acid fast bacilli by A.-F.-G. test decrease along with the improvement of the focus, and such a change does not coincidewitn the culture result.