280 TRANSACTIONS OF SECTION H. 



AU of these manifestations to which I have been calling your attention — the 

 sporadic manifestation of Mongoloid characters in diseased children and in 

 healthy adult Europeans, the generic characters which separate one kind of 

 ape from another, the bodily and mental features which mark the various races 

 of mankind — are best explained by the theory I am supporting — namely, that 

 the conformation of man and ape and of every vertebrate animal is determined 

 by a common growth-controlling mechanism which is resident in a system of 

 small but complex glandular organs. We must now look somewhat more 

 closely into the manner in which this growth-regulating mechanism actually 

 works. That we can do best by taking a glimpse of a research carried out by 

 Bayliss and Starling in the opening years of the present century. They were 

 seeking to explain why it was that the pancreas poured out its digestive juice 

 as soon as the contents of the stomach commenced to pass into the first part of the 

 duodenum. It was then known that if acid was applied to the lining epithelial 

 membrane of the duodenum, the pancreas commenced towork; it was known 

 also that the message which set the pancreas into operation was not conveyed 

 from the duodenum to the pancreas by nerves, for when they were cut the 

 mechanism was still effective. Bayliss and Starling solved the puzzle by making 

 an emulsion from the acid-soaked lining epithelium of the duodenum and inject- 

 ing the extract of that emulsion into the circulating blood. The result was 

 that the pancreas was immediately thro\\Ti into activity. The particular sub- 

 stance which was thus set circulating in the blood and acted on the pancreas and 

 on the pancreas alone, and which thus served as a messenger or hormone, they 

 named secretin. They not only cleared up the mechanism of pancreatic secretion, 

 but at the same time made a discovery of much greater importance. They had 

 discovered a new method whereby one part of the human body could commu- 

 nicate with and control another. Up to that time we had been like an outlandish 

 visitor to a strange city, who believed that the visible telegraph or telephone 

 wires were the only means of communication between its inhabitants. We 

 believed that it was only by nerve fibres that intercommunication was estab- 

 lished in the animal body. Bayliss and Starling showed that there was a postal 

 system. Missives posted in the general circulation were duly delivered at their 

 destinations. The manner in which they reached the right address is of 

 pai-ticular importance for us; we must suppose that the missive or hormone 

 circulating in the blood and the recipient for which they are intended have a 

 special attraction or affinity for each other — one due to their physical constitu- 

 tion — and hence they and only they come together as the blood circulates round 

 the body. Secretin is a hormone which effects its errand rapidly and imme- 

 diately, whereas the growth or morphogenetic hormones, thrown into the 

 circulation by the pituitary, pineal, thyroid, suprarenal, and aenital glands, 

 act slowly and remotely. But both are alike in this : the result depends not 

 only on the nature of the hormone or missive, but also on the state of the local 

 recipient. The local recipient may be specially e;reedy, as it were, and seize 

 more than a fair share of the manna in circulation, or it may have ' sticky 

 fingers ' and seize what is not really intended for local consumption. We can 

 see that local growth — the development of a particular trait or feature — is 

 dependent not only on the hormones supplied to that part, but also on the 

 condition of the receptive mechanism of the part. Hence we can understand 

 a local derangement of growth — an acromegaly or gianti.sm confined to a finger 

 or to the eyebrow ridges, to the nose, to one^ side of the face, and such local 

 manifestations are not uncommon. It is by a variation in the sensitiveness of 

 the local recipient that we have an explanation of the endless variety to be 

 found in the relative development of racial and individual features. 



Some ten years after Starling had formulated the theory of hormones. Pro- 

 fessor W. B. Cannon, of Harvard Universitv, piecing together the results of 

 researches by Dr. T. "R. Elliott and by himself, on the action of the suprarenal 

 glands, brought to Hcht a very wonderful hormone mechanism — one which helps 

 us in interpreting the action of growth-regulating hormones. When we are 

 about to make a severe bodily effort it is necessary to flood our muscles with 

 blood, so that thev may have at their disposal the materials necessary for 

 work — oxygen and blood-sugar, the fuel of muscular engines. At the beginning 

 of a muscular effort the suprarenal glands are set going by messages passing 



