CHAPTER 1 

 INTRODUCTION 



1.1 Discovery of hormones 

 The discovery of hormones v^as a late-comer in the study of 

 physiology ; the circulation of the blood was demonstrated in the 

 seventeenth century by Harvey (1628), but it was more than two 

 centuries before it was realized that chemical messengers could be 

 carried in that circulation. The first hint of this was when Berthold 

 (1849)* showed conclusively that the morphogenetic effects of 

 transplanting the testes of cockerels must be transmitted by some 

 factor in the blood. It was even longer before Oliver and Schiifer 

 (1895) found that a chemical extract of the adrenal medulla, if 

 injected into the circulation, could induce a pronounced rise in 

 blood pressure. In 1901 the active substance in this extract was 

 isolated, identified and called adrenaline. The general term 

 ^'Hormone" is derived from the Greek opfxau), meaning 'T arouse", 

 and indicates the stimulating action of such chemicals ; it was first 

 used by Starling (1905) for secretin, that had been discovered in 

 1902 and shown to induce the flow of alkali from the pancreas. 

 Two hormones concerned with the cure of human disease, 

 insulin for the control of diabetes mellitus, and thyroxine for 

 cretinism, were among the more spectacular discoveries of the 

 early twentieth century, and led to an intensive search for more 

 hormones in man and other mammals. This resulted in the gradual 

 discovery of some thirty kinds of endocrine cells and glands that 

 can produce minute quantities of chemical substances which are 

 carried in the blood, to stimulate or inhibit various specific 

 effectors, or to control different aspects of metabolism and 

 morphogenesis. 



* See Harris (1955) for a translated account of his experiments. 



B 1 



