1) Experiments for obtaining erythromycin resistant strains of M. pneumoniae in vitro were carried out with the use of the Mac strain and the Fukumura strain, which was isolated in our laboratory, and the following results were obtained:
a) Both strains could acquire a high grade of resistance to erythromycin after subcultured serially in broth medium containing erythromycin. With the Mac strain the maximum concentration of erythromycin, in which the growth occurred as rich as the control, observed when the control showed a rich growth, was 200mcg/ml and the maximum growth concentration after one month's incubation was ≥800mcg/ml. With the Fukumura strain the corresponding values were 10mcg/ml and 200mcg/ml.
b) Both strains acquired not only resistance to erythromycin but also cross resistances to the macrolide antibiotics, leucomycin, josamycin, spiramycin, and oleandomycin, and lincomycin as well.
c) The grade of resistances acquired to those antibiotics was different between the two strains.
d) These acquired resistances were stable after passages of the culture through antibiotic-free media.
2) The fermentation inhibition test was performed with the use of both the erythromycin sensitive and highly resistant Mac strains, both of which were sensitive to tetracycline and chloramphenicol, and the following results were obtained:
a) In 17 children with atypical pneumonia, who were bled three times in the course of about three weeks, the growth inhibition titer showed a transient rise to 1:8 to 1:128 with the erythromycin sensitive strain. 16 of them were found to have been given erythromycin on the day when the transient rise was observed. This transient rise was not observed when measured with the erythromycin resistant strain. Five cases to which tetracycline was given did not show such a transient rise with the erythromycin and tetracycline sensitive strain.
b) While the oral administration of josamycin, spiramycin, lincomycin, tetracycline, and chloramphenicol did not elevate the growth inhibition titer of serum measured with the erythromycin sensitive strain, erythromycin, leucomycin, and oleandomycin elevated it up to 1:8 to 1:128. When the erythromycin resistant strain was used, however, such elevation was not observed.
c) If the erythromycin sensitive strain is used in the fermentation inhibition test for the serodiagnosis of M. pneumoniae infection and the second serum, which has not really elevated antibody, is drawn at the time of the administration of erythromycin, leucomycin, or oleandomycin, an erroneous diagnosis may be made. However, such an erroneous diagnosis can be avoided with the use of the erythromycin resistant strain.
d) In cases receiving no antibiotics, the growth inhibition titer of serum was not significantly different between the use of the erythromycin sensitive and resistant strains.
e) The growth inhibiting antibody titer of serum is able to be measured accurately with the use of the erythromycin resistant strain even in the case under administration of macrolide antibiotics. Therefore, it can be concluded that the erythromycin resistant strain of M. pneumoniae should be used for the measurement of the growth inhibiting antibody to M. pneumoniae.

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The mass chest X-ray surveys were made every year on about 70, 000 children of kindergartens and primary, middle, and high schools in Sendai from 1965 to 1969. Growth inhibiting antibodies to M. pneumoniae were measured by the fermentation inhibition test, with the use of the high resistant strain to erythromycin, in paired sera from 1, 032 children consisting of 614 cases of atypical pneumonia and 418 control cares, which were found in the surveys during the five years. The serodiagnostic significance and the course of the growth inhibiting antibody in M. pneumoniae infections were studied in comparison with the complement fixing antibody, and the relationship of the rate of children with growth inhibiting antibody to the prevalence of M. pneumoniae pneumonia was investigated.
1) Of 614 children with atypical pneumonia, M. pneumoniae pneumonia was detected by the significant antibody rise in 41 (6.7%) with the growth inhibition test, and in 32 (5.2%) with the complement fixation test. Thus the rise of antibody detected it in higher rate in the former than in the latter. It was detected in 75 (12.2%) with the complement fixation test when added with cases showing the titer of 1:64 or greater without a significant rise. By the addition of the cases detected by isolation of M. pneumoniae to those by serodiagnosis, M. pneumoniae pneumonia was detected in 86 (14.0%) in total. Of 418 children of the controls, M. pneumoniae infections were detected in 7 (1.7%).
2) In M. pneumoniae pneumonia the cold hemagglutinin titer rose earlier than the growth inhibiting antibody titer and fell rapidly. The growth inhibiting antibody titer rose later than the complement fixing antibody titer and was shown to be maintained for a longer period.
3) In M. pneumoniae pneumonia the more severe symptoms tended to be associated with the higher titer of the growth inhibiting antibody and that of complement fixing antibody.
4) With the complement fixation test it may not make a great error to diagnose the patients with the antibody titer of 1:64 or greater without a significant rise as M. pneumoniae infection. With the growth inhibition test, however, to do so seems to make an error more frequently.
5) The growth inhibiting antibody titer and the complement fixing antibody titer were compared in the first sera from 939 children without the evidence of M. pneumoniae infection. The cases with the higher titer of complement fixing antibody showed the higher rate of the growth inhibiting titer of 1:4 or greater, suggesting the correlation between them. But the reverse correlation was not observed.
6) The rate of children with growth inhibiting antibody was every year the lowest in the first grade of primary school and increased with the increase of the grade. In the second grade of primary school or higher, the more the rate of children with antibody increased, the more the prevalence of M. pneumoniae pneumonia decreased. The annual rate of children with antibody showed a relation to the annual prevalence of M. pneumoniae pneumonia.

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In the experimental study of induced pulmonary carcinoma in rats by administration of N-methyl-N-nitrosourethane (MNU), the developmental process of the coexistent pulmonary fibrosis were revealed. Moreover, the causal relation between the development of pulmonary carcinoma and pulmonary fibrosis was evaluated.
1) Wistar strain rats were repeatedly injected with MNU intraperitoneally, or were alternately injected with MNU subcutaneously or intraperitoneally. In seventy to ninety per cent of rats in the series, the incidence of pulmonary fibrosis was observed.
2) The induced pulmonary fibrosis in the rats was diffuse and interstitial, and the characteristic findings in the fibrosis was fibrous changes centering around the alveolar wall or capillary vessel. In addition, the medial hypertrophy in pulmonary artery and the proliferating connecting tissues in the perivascular and peribronchial areas were remarkably demonstrated.
3) In the cases of sudden death by massive administration of MNU or early death in the chronic experimental group, the marked pulmonary hemorrhage and congestion were observed. In them, the edema and foamy degeneration in pulmonary arterial wall and the perivascular or peribronchial edema associated with cellular infiltration were demonstrated. Therefore, the vascular disturbance may be mainly composed of the cause of pulmonary fibrosis by the administration of MNU.
4) The incidence of pulmonary carcinoma had no relation to the pulmonary fibrosis.

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Two hundred and thirty-seven cases of spontaneous pneumothorax have been reviewed.
While there are several effective methods of therapy, no one method is suited to all cases. With spontaneous pneumothorax of less than 20 per cent, bed rest may be the treatment of choice, since pneumothorax of minor degree will resolve itself with bed rest only in an average of sixteen days.
If sufficient expansion does not occur with bed rest or with needle aspiration, one must resort to other means to obtain expansion and to prevent the complications resulting from chronic pneumothorax. For spontaneous pneumothorax exceeding 20 per cent, or where expansion does not occur with conservative measures, and where initial open thoractomy does not seem justifiable, water seal drainage to reduce morbidity and to prevent recurrence is the treatment of choice.
Thoractomy is the treatment of choice for patients with persistent air leak, chronic pneumothorax, demonstrable multiple blebs or bullae apparent on chest X-ray film, or recurrent pneumothorax.

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