On diseases of the chest : being contributions to their clinical history, pathology, and treatment / by A.T.H. Waters.

Date:
1868
Catalogue details

Licence: Public Domain Mark

Credit: On diseases of the chest : being contributions to their clinical history, pathology, and treatment / by A.T.H. Waters. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    lobulette. The air-sacs of the adult human lung vary in diameter from l-45th to l-85th of an inch. (For illustra- tions of this paragi'aph, see Plate I., figs. 1 and 2.) The walls of which the air-sacs are composed are exceed- ingly thin, and much sacculated; i. e., they have in them a number of small, shallow, cup-like depressions, separated from each other by portions of membrane, which are more or less raised, and project into the anterior of the sacs. The bottom of an air-sac presents the same appearance as its lateral walls; and the cup-like depressions, or alveoli, are there very numerous. The number of these alveoli varies very much ; I have counted as many as ten at the fundus of an air-sac- in a cat's lung; in the human being I have counted five and six, but the number is generally some- what less. I have found the entire number in each air-sac varying from eight to twenty. (See Plate II., figs. 3 and 4.) The air-sacs rest, externally, by their fundus, on the plem-a; but within the substance of the lung they in part rest on, and are supported by, the bronchial tubes and blood- vessels. The air-sacs are separated from each other by thin walls, the membrane composing which, in a lung inflated and dried, is veiy transparent. The projections of this membrane in the shape of thin processes, having a sharp margin, con- stitute the septa between the alveoli; and wherever an open- ing exists leading into a smaller sac, this membrane projects in a similar way, and forms a circular orifice which is much smaller than the cavity to which it leads:—the sac, in fact, dilates abruptly on the distal side of the opening. It is in the membrane composing these walls, and in the septa of the alveoli, that the capillaries of the pulmonary artery are spread out. As I have before remarked, the number of air-sacs beloncr- mg to a lobulette varies: I have counted as many as six