CHAPTER XV 

 MANUFACTURING CELLS 



" The extreme assumption that the laws of Physics and Chemistry are inadequate 

 to explain the causation of vital phenomena is, of course, not justifiable, for it 

 postulates that we fully comprehend now all the laws of the physical world." 



Macallum. 



In the preceding chapter attention has been drawn to the muscles 

 as cell communities which consume poAver but do not produce 

 commodities for the use of the body as a whole. Other cell groups, 

 the glands, may be regarded as industrial communities manufactur- 

 ing goods for use elsewhere. Others again are mere handlers of 

 goods. These latter, the organs of absorption and of 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 secretory 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 is of value 

 to other cells in the body. They secrete into the blood stream. 

 The former may be termed organs of external secretion, or exocrine 

 glands. The latter are called 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 phases — just as 

 we saw that muscle work could be so treated — viz. : {a) Activity, 

 (6) Restitution, (c) Rest or Maintenance. 



(a) Activity. The outsider may gauge the activity of a factory 

 by studying its output, and so, much may be learned of a gland 

 by noting how much it secretes and when. Some glands secrete 

 continuously, others in spurts. With the former, should be 



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