PHYSIOLOGICAL 291 



various members having "a common concern for one another". 

 The consensus partium that the old physiologists and physicians 

 speak of, was attributed in the eighteenth century to pervading 

 "humours" made by various organs, and not always distinguished 

 from the blood itself. While the anatomists began to shift emphasis 

 from the blood to the nervous system as the agency in correlation, 

 increasingly giving the latter the credit, the doctrine of diffusing 

 substances still kept its footing in the more physiological minds. 

 Thus Treviranus, writing about 1801, declares that "each single 

 part of the body, in respect of its nutrition, stands to the whole 

 body in the relation of an excreting substance". Gradually the 

 "humours" were replaced by "internal secretions"; gradually the 

 list of these was criticised and sifted; gradually the different secre- 

 tions — the hormones — have been separated, and their specific 

 effects tested. Even in Invertebrates the discovery of hormones 

 has begun, notably in the pigmented packing-tissue of the leech. 

 Even in plants we begin to hear of them, notably in the ultra- 

 sensitive Mimosa. 



NATURE OF HORMONES.— The word "hormone" (hormao, 

 to stir up), which means excitant, was suggested by Hardy, and 

 accepted by Starling in 1902, as a name for the characteristic 

 product or "chemical messenger" of a ductless gland. "By the 

 term 'hormone' ", Starling said, "I understand any substance 

 normally produced in the cells of some part of the body and carried 

 by the blood system to distant parts, which it affects for the good 

 of the organism as a whole." But as the word hormone was, to 

 begin with, used somewhat widely for any excitant substance in 

 the blood (including carbonic acid!), Sir Edward Schafer proposed 

 the term "autacoid" (which means self -remedy) for the specific 

 products of ductless or endocrine glands. An autacoid is defined 

 as "a specific organic substance formed by the cells of one organ 

 and passed by them into the circulating fluid to produce effects 

 upon other organs similar to those produced by drugs". Since the 

 effects may be in the direction of excitation or in the direction of 

 restraint or inhibition, Schafer proposed to call the excitatory 

 autacoids hormones in the stricter sense, and the restraining or 

 inhibiting autacoids chalones (which means slackening). Biedl has 

 made the interesting suggestion that the former — "erregende Hor- 

 monen" — induce katabolic changes, while the latter — "hemmende 

 Hormonen" — induce anabolic changes; but this has not been 

 substantiated. 



At this point it is historically appropriate, as well as useful for 

 clearness, to refer to the hormone "secretine", which Bayliss and 

 Starling discovered in 1902, and to which they originally applied 

 the term "chemical messenger". Secretine is produced in the presence 



