ANATOMY AND PHYSIOLOGY 



combining with the combustibles it is to consume, it 

 goes without saying that these combustibles them- 

 selves must be carried there also. Nor could it be in 

 doubt that the chiefest of these ultimate tissues, as re- 

 gards quantity of fuel required, are the muscles. A 

 general and comprehensive view of the organism in- 

 cludes, then, digestive apparatus and lungs as the 

 channels of fuel-supply ; blood and lymph channels as 

 the transportation system; and muscle cells, united 

 into muscle fibres, as the consumption furnaces, where 

 fuel is burned and energy transformed and rendered 

 available for the purposes of the organism, supple- 

 mented by a set of excretory organs, through which 

 the waste products the ashes are eliminated from 

 the system. 



But there remain, broadly speaking, two other sets 

 of organs whose size demonstrates their importance in 

 the economy of the organism, yet whose functions are 

 not accounted for in this synopsis. These are those 

 glandlike organs, such as the spleen, which have no 

 ducts and produce no visible secretions, and the ner- 

 vous mechanism, whose central organs are the brain 

 and spinal cord. What offices do these sets of organs 

 perform in the great labor-specializing aggregation of 

 cells which we call a living organism ? 



As regards the ductless glands, the first clew to their 

 function was given when the great Frenchman Claude 

 Bernard (the man of whom his admirers loved to say, 

 "He is not a physiologist merely; he is physiology it- 

 self") discovered what is spoken of as the glycogenic 

 function of the liver. The liver itself, indeed, is not a 

 ductless organ, but the quantity of its biliary output 



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