14 PATHFINDERS OF PHYSIOLOGY 



forty-four years old at the time of Aselli's discovery. Aselli's dis- 

 covery of the lacteals is related by himself as follows : 



"On the 23rd of July in that] year (1622) I had taken a dog in good condi- 

 tion and well fed, for a vivisection at the request of some friends, who very 

 much wished to see the recurrent nerves. When I had finished this demonstra- 

 tion of the nerves, it seemed good to watch the movements of the diaphragm in 

 the same dog, at the same operation. While I was attempting this, and for that 

 purpose had opened the abdomen and was pulling down with my hand the intes- 

 tines and stomach gathered together into a mass, I suddenly beheld a great 

 number of cords, as it were, exceedingly thin and beautifully white, scattered 

 all over the whole of the mesentery and the intestine, and starting from almost 

 innumerable beginnings. At first I did not delay, thinking them to be nerves. 

 But presently I saw I was mistaken in this, since I noticed the nerves belonging 

 to the intestine were distinct from these cords and wholly unlike them, and, 

 besides, were distributed quite separately from them. Wherefore struck by the 

 novelty of the thing, I stood for some time silent while there came to my mind 

 the various disputes, rich in personal quarrels no less than in words, taking place 

 among anatomists concerning the mesariac veins and their function. And by 

 chance it happened that a few days before I had looked into a little book by 

 Johannes Costaeus written about this very matter. When I gathered my wits 

 together for the sake of the experiment, having laid hold of a very sharp scalpel, 

 I pricked one of those cords, and indeed one of the largest of them. I had 

 scarcely touched it, when I saw a white liquid like milk or cream forthwish gush 

 out. Seeing this, I could hardly restrain my delight, and turning to those who 

 were standing by, to Alexander Tadinus, and more particularly to Senator Sep- 

 talius, who was both a member of the great college of the Order of Physicians 

 and, while I am writing this, the medical officer of health, 'Eureka,' I exclaimed 

 with Archimedes, and at the same time invited them to the interesting spectacle 

 of such an unusual phenomenon. And they indeed were much struck with the 

 novelty of the thing." 



Aselli noted the presence of valves in the lymphatic vessels and 

 recognized their function, namely, to prevent the backward flow of 

 the lymph. He recognized also that the lacteals were vessels for con- 

 veying chyle away from the intestine. He went wrong, however, in 

 fregard to the ultimate course taken by the newly-discovered vessels, 

 [ for he thought he could trace them to the liver. Aselli was heavily 

 handicapped by his previous learning, which consisted of a Careful 

 study of as well as veneration for the teachings of the ancienti^ 

 Galen had, in fact, taught that all nutritive material from digestive 

 processes passed through the liver. Aselli speaks in his book of a 

 group of lymphatic glands lying in the mesentery, as the pancreas — 

 hence the name pancreas Aselli. The force which caused the move- 

 ment of the fluid in the lacteal vessels was believed by him to be two- 

 fold, a vis a tergo and a vis a f rente ; the latter derived from supposed 

 suction of the liver and the former supplied by the movements of the 

 intestines. 



Aselli Opposed by Harvey. Aselli in his modesty endeavored to 

 prove that the lacteals were known to the ancients, especially to 

 Herophilus and Erasistratus, founders of the Alexandrine school of 

 medicine. His discovery met the same opposition as did Harvey's, and 

 from the same men, among them Riolan and Primrose, and strange to 

 say Harvey himself failed to recognize the importance of the work 



