THE STORY OF NINETEENTH-CENTURY SCIENCE 



tion in passing through the liver. The liver cells (the 

 peculiar forms of which had been described by Purkinje, 

 Henle, and Dutrochet about 1838) have the power to 

 convert certain of the substances that come to them into 

 a starchlike compound called glycogen, and to store this 

 substance away till it is needed by the organism. This 

 capacity of the liver cells is quite independent of the 

 bile-making power of the same cells ; hence the discov- 

 ery of this glycogenic function showed that an organ 

 may have more than one pronounced and important 

 specific function. But its chief importance was in giv- 

 ing a clew to those intermediate processes between di- 

 gestion and final assimilation that are now known to 

 be of such vital significance in the economy of the or- 

 ganism. 



In the forty-odd years that have elapsed since this 

 pioneer observation of Bernard, numerous facts have 

 come to light showing the extreme importance of such 

 intermediate alterations of food-supplies in the blood as 

 that performed by the liver. It has been shown that 

 the pancreas, the spleen, the thyroid gland, the supra- 

 renal capsules are absolutely essential, each in its own 

 way, to the health of the organism, through metabolic 

 changes which they alone seem capable of performing ; 

 and it is suspected that various other tissues, including 

 even the muscles themselves, have somewhat similar 

 metabolic capacities in addition to their recognized func- 

 tions. But so extremely intricate is the chemistry of 

 the substances involved that in no single case has the ex- 

 act nature of the metabolisms wrought by these organs 

 been fully made out. Each is in its way a chemical 

 laboratory indispensable to the right conduct of the 

 organism, but the precise nature of its operations re- 



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