Report on the progress of human anatomy and physiology in the year 1842-3 / [Sir James Paget].

  • Paget, James, Sir, 1814-1899
Date:
1844
Catalogue details

Licence: Public Domain Mark

Credit: Report on the progress of human anatomy and physiology in the year 1842-3 / [Sir James Paget]. Source: Wellcome Collection.

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    As to the action of the diaphragm, the authors believe that it produces, l. Elon¬ gation of the thoracic cavity, especially in the abdominal type of respiration. 2. Increase of the transverse diameter, by elevating and turning outwards the lower ribs, as in the experiment quoted in a preceding note; and this especially in the inferior costal respiration. 3. Occasionally, in infants, the depression of the costal cartilages. The second of these actions of the diaphgram is also described by M. Magendie.* The true mode of action is probably this: when the muscular fibres of the diaphragm contract, its central portion descends, and at the same time traction is exercised on the ribs at the peripheral ends of the fibres; and when the resistance to the descent of the diaphragm is greater than the resistance to an upward motion of the ribs, these are raised by the fibres which are attached to them, and whose direction, even in moderate inspiration, is nearly vertical. And this drawing upwards of the ribs is necessarily converted into a movement upwards and outwards by the limited and peculiar mobility of their attachments to the vertebrae and sternum. The third assigned action, that of the occasional depression of the inferior costal cartilages in children, is more reasonably ascribed by Mr. Alexander Shawf to this, the most pliant part of the walls of the chest, being pressed in by the atmosphere when the other parts of the chest are expanded to a size which the lungs cannot attain, on account either of disease of their structure, or of obstruction to the free entrance of air through the larynx and trachea. Structure of the Lungs. Mr. Addison^ has given an account of the anatomy of the minute air-passages which, while it confirms nearly all that Reisseissen observed, is more complete, and very probably true. In the foetus the ultimate bronchial subdivisions are tubular ; they have a regularly branched arrangement, ramifying symmetrically in all directions, and terminating without anastomoses in closed extremities which are generally situated attheboundariesofthe lobules. But when an animal has respired, the entrance of the air into the lungs distends the lobules, and the ultimate bronchial subdivisions undergo a great change. The mem¬ brane composing each of them offers only a feeble resistance to the pressure of the air, and is pushed forwards and distended laterally into rounded inflations, forming a series of communicating cells, which meeting on all sides those of the adjoining bronchial subdivisions, are moulded by the mutual pressure into various hexagonal and pentagonal forms These distended passages (something like large beaded tubes) Mr. Addison calls lobular passages ; and a section of them shows the oval foramina leading from cell to cell, which are so conspicuous in a thin layer of inflated and dried lung. The air-cells, according to this account, are the inflated parts of the intralobular bronchial subdivisions ; and those of each lobule form a distinct system, having no communication with those of the adjacent lobules, except in the common trunk from which the intralobular bronchi of each system are derived. The air-cells are from 1-200 to 1-500 of an inch in diameter; and the oval foramina are from 1-60 to 1-150 of an inch or less in diameter. The blood-vessels lie upon each lobular passage, and between each two of them. Capacity of breathing. M. Bonrgery’s examinations of the structure of the lungs are detailed in vol XIV, p. 546. They may easily be reconciled with the more probable account of Mr. Addison, from which they chiefly differ in that the minutest branches of the bronchi are described in them as freely anastomosing, so as to form a series of labyrinthic canals; and that the constrictions of the tubes by which they are formed into cells or loculi are said to be due to annular vessels surround¬ ing them. M. Bourgery§ has more recently examined the relations of the varying structure of the lungs in different ages and sexes to their functional capacity. The subjects examined were fifty males and twenty females, and the deductions are as * Precis d » Physiologie, p. 310. t London Medical Gazette, Oct. 29, 1811. I Philosophical Transactions, Part ii, 1842. An abstract, from which the above is taken, is in the Trans, of the Prov. Med. and Surg. Association, 1843, vol. xi, p. 281. § Paper read at the Academie des Sciences, Janvier 23, 1843 ; Arch. Gen. de Made¬ line, Mars, 1813 ; Gazette Medicale, and other French journals of the same date.