Note 67 — Chapter II · OF THE INFLUENCE OF THE DEATH OF THE HEART, OVER THAT OF THE BRAIN.

When air is introduced into the vena portæ, there is not only no ill effect at the moment of injection, but there usually follows no apparent effect on the animal. It is not the same when air is injected into the veins of the general system, with so much care as not to produce instantaneous death by the dilatation of the heart. The effects do not then appear till a long time after the injection; but they are wholly different from the primary effects which we have described.

These consecutive symptoms from the entrance of air into the veins are, as Nysten has remarked, the result of an obstruction of the lungs produced by the accumulation of air in the last divisions of the pulmonary artery. The embarrassment in respiration often appears at the end of half a day, it becomes greater and greater, the bronchiæ are filled with a viscid fluid; and the animal usually dies on the third or fourth day. On examination of the body, no air is found in the heart or the vessels; but the lungs, instead of being pink-coloured, are greyish, tinged with brown, and loaded with frothy blood and mucus.

Boerhaave thought, that death which follows the injection of air into the veins was always owing, as it is in this case, to the presence of the air, which offers, in the small vessels, a mechanical obstacle to the passage of the venous blood.