The comparative fat content of the portal vein as determined by the presence of fat particles with the darkfield microscope

Although it is generally stated that not all of the fat ingested can be recovered from the thoracic duct, there is no very satisfactory evidence to show that fat is absorbed directly into the blood under normal conditions. Fat absorption through the villi into the lacteals and thoracic duct as the “molecular basis of chyle” and the entrance of these minute particles (chylomicrons) into the venous system has been known since the time of Boyle, Hewson and Gulliver, and is not difficult of demonstration.

The use of the darkfield microscope has been of distinct value in studying the increase and decrease of the chylomicrons during, and after, the period of fat absorption with the use of the ocular micrometer, following the method of Gage for counting these minute particles with approximate accuracy.

In connection with other study upon fat absorption, observations were made upon the chylomicron content of the blood of the aorta, jugular and portal veins at different periods of digestion with results as shown in the following table:

Following the course of the circulation, it should be noted that the liver has a double source of supply of these particles: (1)through the hepatic artery and (2) through the portal vein, the origin of which is principally from the capillaries of the mesenteric arteries in the villi of the intestine.

The result of the blood examinations was rather unexpected for it might naturally be assumed that the fat particles, distributed throughout the circulation, would be represented in the portal vein to the same extent as in the blood of other parts of the body, or if there were direct absorption into the Blood even in greater numbers. In the majority of the cases the counts showed quite a distinct decrease in the number of the fat particles in the portal vein as compared with the jugular vein or aorta.