Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 1, 1802).djvu/66

42] circulating to every part of the body. But, on rising to come ashore, the blood makes its way again through the lungs, as soon as the animal begins to respire.

As in all land animals a large portion of the mass of blood continually circulates through the lungs, which would be stopped, if the free access of air were excluded; so we find in fish a great number of blood-vessels passing through the gills, which must be perpetually wet, lest the blood should, in like manner, be checked, and consequently stagnate in its progress. Hence, when the latter are removed from their natural element, the branchiæ very soon grow crisp and dry, the vessels become corrugated, and the blood finds no outlet: likewise, when land-animals are immersed under water, or in any other manner deprived of respiration, the circulation ceases, and the animal inevitably dies.

Inquisitive physiologists have advanced, that  may, by art, be rendered amphibious, and enabled to live under water, as well as the beaver, or turtle; because the fœtus in utero lives without air, and the circulation is continued by means of the oval hole: if, therefore, this important opening could be preserved after the birth of the child, the same useful faculty might still remain.

This proposition is plausible; and we do not hesitate to declare, that in a maritime country, such attempts ought by all suitable means to be encouraged: for the advantages resulting from a successful application of the theory, would indeed be incalculable. In its support, and as an instance of the wonderful power we possess over the organs of respiration, it may be urged, that expert divers feel no inconvenience from remaining for several minutes under water, at a considerable depth; that individuals affected with asthma (among whom the writer of this article is a living evidence) have by mere force of habit obtained effectual and permanent relief in that distressing complaint, by accustoming themselves from the commencement of it, to respire principally through the nostrils, whether in a waking or sleeping state; and lastly, that none of the interior organs possess a flexibility and power of expansion (unattended with loco-motion) equal to those of respiration.

After this short digression, we shall proceed to state the means by which that desirable faculty of respiring under water, may be acquired by the human subject.

It should previously be remarked, that the lungs of the embryo are compressed during its confinement, so that the pulmonary blood-vessels are impervious, and consequently the circulation must take place through the oval hole, and the arterial canal before-mentioned: hence the amphibious animal and the fœtus in utero are so far analogous in their nature; and though this hole generally closes at an early period of infancy, yet there are instances, well attested by anatomists, where it has been occasionally found not quite closed in human subjects, who have died at an advanced age. There is, however, one material difference between them: the fœtus never having respired, is sufficiently nourished by the maternal blood circulating through its whole body, which progressively grows, till its birth, without feeling the want of respiration during the whole period of nancy,