THE STRUCTURE OF THE RESPIRATORY TISSUE IN THE NEWLY-BORN

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Abstract
The lungs of newborn mammals are not a miniature of the adult''s lung. The degree of pulmonary development varies with the general bodily development at birth. This statement is likely to apply to all newborn mammals and it is apparent that the new-born infant represents only one link in the chain leading from the fetal to the more mature newborn mammals. An important difference between the newborn infant and newborn animals is the great number of generations of respiratory bronchioli in the infant. It is, therefore, suggestive that the lung of newborn animals is much more a miniature of the lung of the adult animal than it is in man. The large number of respiratory bronchioli in the infant is later reduced to 2 or 3. It follows that the lung in man grows much more by the formation of new acini in the course of the first few years than is the case in animals.