n] Circulation of the Blood. 49 



"On the 23rd of July of that year (1622) I had taken a 

 "dog in good condition and well fed, for a vivisection at the 

 " request of some of my 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 intestines and stomach gathered together into a mass, 

 " I suddenly beheld a great number of cords as it were, 

 " exceedingly thin and beautifully white, scattered 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 that I was 

 " mistaken in this since I noticed that 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 into my mind 

 " the various disputes, rich in personal quarrels no less than in 

 " words, taking place among anatomists concerning the mesaraic 

 " 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. ,1 had hardly touched it, 

 " when I saw a white liquid like milk or cream forthwith 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 Septalius, 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 detected the presence of valves in these vessels and 

 recognised that they hindered the backward flow. He saw 



p. l. 4 



