CYCLE OF ACriVITV 183 



placed the endocrine organs, with the latter, the digestive glands. 

 Of course those which maintain a steady output may, under 

 stress, greatly accelerate their rate of secretion, and of the latter 

 class the salivary glands at least maintain normally a level of 

 secretion which under a suitable stimulus is enormously increased. 

 There seems no doubt but that the industrial cell-group consists 

 of four different parts corresponding to their activities. (I.) The 

 factory itself where the secretion is prepared. (II.) The store room 

 where it is packed and kept in bulk. (III.) The dispatch depart- 

 ment where it is first packed small and ready for delivery and then 

 (IV.) the actual delivery department. Generally when we speak of 

 the activity of a gland we refer exclusively to this last function, 

 viz., active secretion. What then regulates the rate of secretion ? 

 The same factors come into play w^hich operate in our industrial 

 world, viz. : 



1. Stock on hand. 



2. Rate of output from workshop. 



3. Efficiency of the dispatchers. 



4. Demand for goods. 



Normally, the store of goods on hand and the rate of manu- 

 facture do not materially influence the output. Of course, if the 

 operatives are poorly nourished or badly supplied with raw 

 material, then output will fall. Under certain pathological condi- 

 tions, a state of temporary or chronic over-production occurs. 

 Similarly, insufficiently fed or overworked dispatchers will perform 

 their duties half-heartedly and output will be decreased, but as a 

 rule this factor does not come into play. 



The decisive element controUing rate of output is the demand for 

 goods. The store of goods is draw^n upon and the factory speeds 

 up to replenish the store. If the stored material is sent out more 

 rapidly than it can be replaced, then overtime has to be worked 

 in the factory, and if persisted in, industrial fatigue is caused and 

 total cessation of work is the final result (cf. Secretion of Milk). 



These various conditions may be studied conveniently by 

 studying the intake of oxygen or output of COg. In some instances 

 the intake of potential energy may be measured. From these 

 it is found, as in muscle, that a very small proportion of the 

 total Og intake goes to the dispatch department. That is, the 

 actual setting free of the secretion does not require much energy, 



{b) Restitution. Just as in muscular, so in glandular activity 

 the great proportion of the oxygen used is associated with the 

 phase of restitution. Energy is required for the building up of 

 material to replace that lost during secretion. 



