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Changes occurring with increasing age in the rat lung: Morphometrical study

Background: It was hypothesized that the evolution towards the senile lung is progressive, being initiated in the adult stage; and for this reason changes similar to those described in the senile lung can be detected in the lungs of middle‐aged rats. To test the hypothesis, the following design was used. The lungs of two groups of rats, adult (mean age of 16 weeks) and middle‐aged (mean age of 56 weeks) were morphometrically compared.