CHAPTER XIV 

 MANUFACTURING CELLS 



" For know, whatever was created needs 

 To be sustained and fed ; of elements 

 The grosser feeds the purer." 



MILTON. 



IN the preceding chapter attention has been drawn to the 

 muscles as cell communities which consume power but do not 

 produce commodities for the use of the body as a whole. Other 

 cell groups, the glands, may be regarded as the industrial com- 

 munities manufacturing goods for use elsewhere. Others again 

 are mere handlers of goods. These latter, the organs of absorption 

 or excretion (negative absorption), do not as a rule alter the 

 chemical state of the material, raw or manufactured, that they 

 handle. They accept delivery, repack in suitable containers it 

 may be, and forward for transport. 



The glands may be divided for convenience into two classes. 

 First, those which by means of a duct, opening outside the body, 

 secrete manufactured material. The glands of the alimentary 

 tract and the skin glands (sweat and milk) belong to this class. 

 The other class prepares material which itself is used by the 

 body cells. They secrete into the blood stream. The former 

 may be termed organs of external secretion, the latter organs of 

 internal secretion, ductless glands or endocrine organs. 



As far as is known the principle underlying the activities of 

 all glands is the same. Each manufactures some material which 

 is stored up, and when wanted this material is washed out by a 

 stream of water. That is, they all consist of a workshop and a 

 dispatch department. These two functions are seemingly under 

 different control and have to be studied separately. 



The work done by a gland may be divided into three phases 

 just as we saw that muscle work could be so treated viz. : 

 (a) Activity, (b) Restitution, (c) Rest or Maintenance. 



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