vi] Sylvius and his Pupils. 157 



juices with the chyle would interfere with the effervescence ; 

 but he argues that dilution may favour effervescence. " We 

 " answer," says he, " that oil of vitriol mixed with water excites 

 " a far more violent effervescence with iron filings than when it 

 " is used pure without any water." So completely did Sylvius 

 and his school identify physiological fermentation with chemical 

 effervescence. 



Confident as Sylvius and his pupil were of the occurrence 

 and of the importance of this effervescence of pancreatic juice 

 and bile, they were far from clear as to how it promoted 

 digestion. De Graaf gives two uses. The effervescence in the 

 first place attenuates the viscid mucus lining the interior of the 

 intestine, the presence of which might hinder the absorption of 

 chyle by the lacteals ; and in the second place it assists the due 

 separation of the useful parts of the food from the useless. But 

 he does not explain how it does this. It is interesting to note 

 that he attributes, the white colour observable in the duodenum 

 beyond the entrance of the pancreatic duct to the pancreatic 

 juice. "As regards," says he, "the whitish colour observable in 

 "the more fluid parts of the food, we think that is due to 

 " the acidity of the pancreatic juice, for we have observed that 

 " many other things abounding in lixivious (soluble) salt and oil 

 " whiten upon the addition of acids." Here again we see how 

 completely the school of Sylvius identified physiological changes 

 with changes of a purely chemical nature. 



In the time of Sylvius men's minds were full of the discovery 

 of the lacteals, the thoracic duct and the lymphatics, and 

 Sylvius had no manner of doubt that all the chyle, that is to 

 say, all the nutritious parts of the food, passed into the lacteals 

 and were so discharged into the venous system through the 

 thoracic duct. The blood carried to the right heart by the 

 upper great veins was in his view chylous blood. In the right 

 side of the heart it met with the blood of the vena cava, and 

 this Sylvius speaks of as bilious blood. Following the idea 

 which van Helmont seems to have held that bile is secreted by 

 the gall-bladder, Sylvius warmly espoused a view which had 

 been recently put forward, that that part of the bile which was 

 not needed for digestion was carried back to the liver, where 



