21 8 HEREDITY AND EUGENICS 



putting the body into a state of defence in the most 

 marvellous wa\^ The substance adrenalin is derived 

 from the medulla of the adrenal glands. It has been 

 chemically synthesised, and Schaefer showed that 

 when injected into the veins it raises the blood- 

 pressure. Its concentration in the blood is only about 

 I part in 20,000,000, and 100,000 times this quantity 

 is held in the gland ready for emergencies. Cannon 

 showed that w-hen secreted into the blood, as a result 

 of the emotions of fear or anger, it prepares the body 

 for mortal combat by summoning its reserves and 

 increasing its defences. It stimulates the liver to pour 

 out more carbohydrates. The blood is thus flooded 

 with sugar which can immediately be used as fuel for 

 the body in exertion. The number of red corpuscles 

 in the blood is also increased, the blood is withdrawn 

 from the skin and viscera and sent to the muscles, 

 heart, lungs, and central nervous system. The limbs 

 actually grow larger wdth their increased blood suppl}^ 

 the heart beats faster, and the senses are keener; the 

 effects of fatigue are abolished, and the blood is 

 rendered more coagulable. All these purposive re- 

 actions of the body depend upon the presence in the 

 blood of a shghtly increased amount of adrenalin. 

 The administration of adrenalin to animals also 

 causes their blood to clot more quickly, erects their 

 hair, and dilates their pupils. Adrenal excess, due 

 to hypertrophy of the cortex, causes high blood 

 pressure, and in w^omen a tendency to masculinity. 

 Depletion of the adrenal reserves, on the other hand, 

 leads to the conditions know^n as neurasthenia, 

 nervous breakdown, chronic fatigue, and shell shock. 

 If differences in endocrine activity are characteristic 

 of the races of mankind, then such differences are 

 inherited. Are smaller glandular differences between 

 the individuals of the same race inherited ? This 

 thesis is supported by Berman (i 921) in a book on the 



