ABSTRACT
The start of the Tertiary period saw mammals overtake and eclipse reptiles as the dominant terrestrial vertebrate group. Lungs of high-altitude mammals have greater diffusing capacities for oxygen than those of sea-level dwellers. Lobectomy induces compensatory growth, with the remaining lobes soon attaining the initial diffusing capacity for oxygen. Among vertebrates, the mammalian lung has been best studied structurally and functionally. The human lung in particular, without valid justification, is assumed to be a model of the vertebrate lungs. Compared with the avian lung, the mammalian lung developed much earlier from the complex multicameral reptilian lung. The bronchial system of the mammalian lung branches progressively, terminating in the rather hexagonal air cells termed the alveoli. Lungs of high-altitude mammals have greater diffusing capacities for oxygen than those of sea-level dwellers. Lobectomy induces compensatory growth, with the remaining lobes soon attaining the initial diffusing capacity for oxygen.
