738 METABOLIC PROCESSES [BOOK n. 



How little we know concerning the metabolism of the master 

 tissues themselves was shewn when we were dealing with these 

 tissues in an earlier part of this work ; but success in the study of 

 these can hardly be expected until our knowledge is increased as 

 regards the changes which the blood undergoes before it reaches 

 and after it leaves the muscle or the nerve. The fact that a large 

 part of the absorbed food is carried through the liver before it is 

 thrown on the general circulation leads us to suppose that in this 

 large organ important metabolic processes are carried on ; and 

 observation with experiment confirms this view. Important as 

 the secretions of bile may be the other metabolic functions of the 

 liver are of still greater importance ; and preparatory to the study 

 of these we may now take up the structure of this organ. 



