Volume 2

The anatomy and physiology of the human body.

  • Bell, John, 1763-1820.
Date:
1826
Catalogue details

Licence: Public Domain Mark

Credit: The anatomy and physiology of the human body. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    or rather one might be apt to mistake them for nerves. Of the way in wliich tliis function is jierformed, there must be more varieties than we can know or comprehend: this we may safely conclude from the little that we do know, finding the variety so very great. Almost all insects, with the exception of dipterous larvai, have their puncta like those of the Caterpillar, ranged along the side, and inosculating from branch to branch : often the puncta open along the sides ; but in place of inosculating from branch to branch, all round one side, they inosculate across the belly, the one side communicating with the other. This is best observed in the small larva from which the Bee proceeds. And here it must be observed, that, as in insects, with the exception of dipterous, always the stigmata or breathing points correspond neatly with the folds or rings while it continues a larva, and with the segments or divisions of the body when it becomes a Fly ; in the Bee-worm also the inosculations answer to the joint of the body. Sometimes when an insect lives in water, it has only two puncta respiratoria: these puncta begin either in the snout or in the tail j they are the open- imrs of two ffreat air tubes which run down each side of the insect like two aortas, and the insect has means of rising to the surface, takes down a bubble of air along with it, and discharges a bubble of air before it rises again; of this nature are the air tubes of that Worm from which the Ephemeris proceeds. The two great air tubes are seen like two aortas run- ning all along the body, and their minuter branches are seen ramifying beautifully upon the abdominal muscles and other parts. Many insects are aquatic when first they are hatched from the egg. They have little gills which serve them while they continue in the water, as, for exainjile, the larva of the Ephe- meris Fly. These little gills are fringed with micro-