The diaphragm in man : a record of our present knowledge of its development, relationships, structure, and mode of action / by J.F. Halls Dally.

  • Dally, John Frederick Halls, 1877-1944.
Date:
[1908?]
Catalogue details

Licence: In copyright

Credit: The diaphragm in man : a record of our present knowledge of its development, relationships, structure, and mode of action / by J.F. Halls Dally. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    JI. GENERAL VIEW OF THE FUNCTION OF RESPIRATION. Respiration, being essentially organic, exists in the vegetable and animal worlds alike, its object being the intake of oxygen and the elimination of carbon dioxide. The chemical and mechanical methods by which these processes take place differ widely, being initiated in animals by invagination of epiblast derived from the digestive tract. According to Darwin(^), all physiologists admit that “the swim-bladder is homologous or ideally similar in position and structure with the lungs of the higher vertebrate animals,” and further, “ in certain fish the swim-bladder seems to be nearly rudimentary for its proper function of giving buoyancy, but has become converted into a nascent breathing organ or lung ” 0. Hence, since natural selection shows that there is no logical impossibility in this and other striking functional changes, it may be admitted that all vertebrates, at some period of their existence, have two distinct modes of breathing. In all vertebrates, gills or their representatives are present during embryonic existence; “in the fish and a few reptiles the gills are permanent, but in others they disappear, and, while traces of a lung are seen in all vertebrates, they acquire full develop- ment only in reptiles, birds and mammals; while again, certain amphibians, such as the proteus and siren, retain both gills and lungs to adult life, and thus form a link between fishes and reptiles ” (^). In the human embryo cephalic visceral clefts are present, the lowest three of these representing the gill-clefts of fishes and amphibia. In birds and mammals these clefts are not as a rule developed into complete apertures(^), and in Amniota appear to remain closed throughout foetal life (=). “ In some fishes the branchial arches and clefts are more numerous than in other vertebrates, and in a few the hyoid arch also develops a gill ” (®). The fourth and fifth visceral arches may be considered to belong to the neck rather than to the head. The simplest form of direct aeration of the blood by means of lung-structures is seen in reptiles which have large simple sacs into which the air is introduced by deglutition. In birds the apparatus is more elaborate, since the sacs are subdivided into lobules. The mammalian respiratory system consists of:— 1. An osseous framework—the thorax. 2. Systems of opposing muscles—