CHAPTER VI 

 THE BIO-ECONOMICS OF INTERNAL SECRETIONS 



THE subject of internal secretions is coming into great prominence 

 in Physiology. Mr. P. G. Stiles tells us in the Scientific American, 

 Supplement, No. 2,169, that it will doubtless occupy a larger 

 and larger place in future expositions of Physiology. This is 

 what we are told by way of introduction to the subject : 



One need not be a profound student of science to appreciate that 

 the co-ordination of activities is a most striking fact of animal life. What 

 happens in one place is adapted to what is occurring at another. It may 

 fairly be claimed that each part acts more distinctly for the good of the 

 whole than for its own advantage. Clearly, this could not be the case 

 if there were not some mode of transmitting influences from organ to organ. 

 When one considers the possible means of such transmission, the nervous 

 system is at once suggested. This wonderful structure is so fashioned 

 that, conceivably, any part of the body may definitely affect any other. 

 It is in this respect like a telephone exchange which affords to each sub- 

 scriber the opportunity to communicate with any other. The nervous 

 system has long been looked upon as the essential instrument of co-ordina- 

 tion. A second possibility has lately become unexpectedly prominent. 

 It is the transmission of chemically active products through the medium 

 of the circulation. Such products of the tissues are usually called internal 

 secretions. A compound added to the blood by one organ, will, within 

 a minute, be quite uniformly diffused over the whole body. There is no 

 way to limit its distribution and bring it all to bear upon a restricted 

 portion of the system. In this respect the interchange of influences by 

 means of internal secretions lacks the refinement and precision which 

 characterise the nervous correlation. We have to do with a set of drugs 

 which, like those administered by the physician, must be offered to all 

 the tissues to those which seem indifferent as well as to those which 

 are evidently responsive. 



It is clear that Mr. Stiles visualises the internal or " physio- 

 logical " economy of the animal as constituting essentially a 

 case of Symbiosis. There is at least in normal days, we may 

 assume, a pronounced systematic reciprocity between the parts. 

 If it can be said that " each part acts more distinctly for 

 the good of the whole than for its own advantage," then we 

 have here, not a mysterious altruism, but a symbiotic sub- 

 ordination of minor autonomies to superior autonomy. The 



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