The terminal distribution of the hepatic artery

The following conclusions were arrived at on the terminal distribution of the hepatic artery and its microscopical structures in the experiments conducted with the livers from human adult, fetus, dogs and toads, to which were given plastics, Indian ink and Indian-ink shock injections into their hepatic blood vessels. 1. There are arterial anastomotic networks of vasa vasorum in the portal wall. 2. The intralobular arterioles (Elias) and the extralobular arterioles (WEATHERFORD) often arise as direct branches without passing through the periductal arteriolar plexus. In the peripheral zone of the liver, this constitutes the main type of origin. 3. Besides the anastomoses between the intralobular arterioles of the adjacent lobules (Fig. 5), the periductal arteriolar plexus of the bile ducts to the neighboring lobules are interconnected by arterial branches surrounding the interlobular vein ("neighboring arteriolar anastomoses" by the author) (Figs. 2, 5). 4. The terminal arterioles reveal a curve and an isthmus (Figs. 1, 3, 5), where they are supposed to have epithelioid cells in the media. 5. The hepatic vein wall is supplied by the branches of the internal thoracic and phrenic arteries. These anastomose with the interlobular arteries in the interdigitation area of vessels. 6. In the toad the terminal distribution is of a simpler form, in which the arterial capillaries, with an S or a parabolic curve, being constricted by the marginal hepatic cells, join the sinusoid in capillary form. 7. In human fetus of the middle stage (Figs. 6, 7), most of the terminal arterial capillaries open directly to the interlobular hemopoietic tissue, and from there the blood flows into the sinusoid. The precapillaries have an S curve and an isthmus, where they have 3 or 4 primordial epithelioid cells. In other portion, the precapillaries form endothelial canals with little adventitia and open infundibularly to the hemopoietic tissue. These have been proved by the Indian-ink shock injection method. 8. In the fetus of the later stage (Figs. 8-11), with the reduction of interlobular hemopoietic tissue, its arterial branches become fewer, and many branches are connected directly to the hepatic sinusoid. They form a sharper S curve and an isthmus, where 4 or 5 epithelioid cells are differentiated. The arterial terminal branches are precapillaries of endothelial canals having little adventitia and no media muscle. 9. The subcapsular branches of the peripheral interlobular arteries anastomose with one another. Besides these, subcapsular branches come around the hilar region from the hepatic artery, furthermore some are derived from the biliary, inner thoracic, diaphragmatic, intercostal, subcostal, suprarenal and renal arteries. Anastomoses are found between all the subcapsular branches of different origins.