v] of Chemical Physiology. 139 



caecum with a stercoraceous ferment by which it is converted 

 into faeces. 



Such in brief outline is van Helmont's story of what even 

 now-a-days we sometimes call primary and secondary digestion. 



The fourth digestion takes place in the heart and arteries. 

 By this elaboration the darker and thicker blood of the vena 

 cava becomes lighter in colour and distinctly volatile. By this 

 he obviously means the change from venous to arterial blood. 

 But he does not very clearly distinguish between this fourth 

 digestion and his succeeding fifth digestion, "which changes the 

 blood of the arteries into the vital spirit of the archceus." He 

 distinguishes between the crude blood (cruor) supplied by the 

 liver and the vitalized blood (sanguis) distributed by the heart 

 through the arteries. 



" I never could satisfy myself," says he, " that there was any 

 "spirit in the crude blood (cruor) coming from the liver, 

 41 though this had already acquired its own grade of perfection 

 "after it had left the mesentery. The crude blood from the 

 "liver has always seemed to me mere material for use; it 

 "ought not to be considered as perfect vital blood." 



His view seems to be that by the time it reaches the 

 arteries the crude material blood has become vitalized blood, 

 through the presence of the spiritus vitalis. This spiritus is of 

 the nature of or acts after the fashion of a ferment, it multiplies 

 itself as a ferment does. It is always present on the left side 

 of the heart, in the arterial blood of the left ventricle, and some 

 of it is drawn through the septum, from the left side to the right 

 by minute pores which are too minute to allow blood to pass. 



11 Some of this spiritus," says he, " this ferment, thus drawn 

 * through the septum begins to multiply even on the right side 

 " of the heart. The right side of the heart labours incessantly 

 " for no other end than that it should draw a little spiritus 

 "from the left side across the septum of the heart in order 

 "that the crude blood in the vena cava close to the heart 

 "should by the participation of that spiritus at once begin 

 "to be vivified." 



Apparently the fourth digestion is only the beginning or a 

 part of the fifth digestion, which as a whole consists in the 



