Page:The growth of medicine from the earliest times to about 1800.djvu/429

 At a still earlier date (1622) Caspar Aselli of Cremona, Northern Italy, professor in the Medical School of Pavia, discovered the chyle ducts. This discovery was made under the following circumstances, which reveal the fact that good luck sometimes plays an important part in the work of the searcher after truth in the departments of anatomy and physiology:—

Aselli was studying the distribution of the recurrent nerves and the movements of the diaphragm in a well-nourished living dog, when his attention was drawn to the presence of a large number of delicate white threads coursing as it were over the surface of the mesentery. Following the accidental injuring of one of these threads there escaped from the wounded structure quite a large quantity of chyle. Aselli, who instantly appreciated the full significance of what had happened, exclaimed, in the presence of the bystanders, "Eureka!" At the time he supposed that these chyle vessels terminated in the liver and contributed in some manner to the elaboration of the blood (in harmony with Galen's universally accepted theory of sanguification); but later, after he had carried out a carefully conducted series of experiments, he was able to rectify this erroneous belief. (Haeser.)

Galen's theory of sanguification may be stated as follows: The chyle is received into the veins of the intestinal wall and carried thence to the liver, in which organ they are all gathered together into a single venous trunk which has received the name of "vena portae"—the vein of the gate-*way. Everything that is destined to enter the liver passes through this portal vein. In the organ itself the chyle undergoes certain modifications, the result of which is, first, to deprive it of its impurities and then, in addition, to effect other changes that convert it into blood. Aselli's glory, then, consists in his having shown that chyle is taken up from the intestinal mucous membrane by a set of its own vessels, and not by the veins, as taught by Galen.

In 1651 Olaus Rudbeck of Arosen, Sweden, discovered the lymphatics of the intestinal canal and followed their distribution into the lymph nodes; he also established their relations with the thoracic duct and with the venous system.

Thus, thanks to the series of brilliant discoveries made