14(5 PHYSIOLOGY OF FARM ANIMALS [CH. 



Brown-Sequard showed that removal of the sujirarenals 

 caused death in shorter time than removal of the thyroids. 

 The symptoms preceding death were great muscular weakness, 

 intense prostration, and loss of vascular tone. These are the 

 symptoms of Addison's disease which is a disease of the supra- 

 renals. Oliver and Schafer showed that extract of these organs 

 when injected into the circulation causes a very marked rise of 

 blood pressure, caused by the contraction of the peripheral 

 arteries. If the vagi are then cut or paralysed, the heart's action 

 is enormously accelerated and strengthened. Elliott and others 

 have shown that the extract acts upon the sympathetic fibres of 

 the vessels, and there is a special connection (developmental as 

 well as functional) between the suprarenal medulla and the 

 sympathetic system. The effect of suprarenal extract in con- 

 stricting the arteries is taken advantage of by surgeons and 

 others to stop bleeding or inflammation, but in the latter case 

 the effect is transient and continues only so long as the active 

 principle is present. 



The active principle of the suprarenal glands is called adrenalin. 

 It is produced only by the medulla, the function of the cortex 

 being problematical. Adrenalin has the empirical chemical 

 formula CgHjgNOg. It was first synthesised by Takamine and 

 Aldrich. It is of the nature of a hormone and is necessary for 

 the normal metabolism of the muscles on which it acts through 

 the sympathetic nervous sj'stem. Absence of the secretion causes 

 loss of muscular tone and vigour, as exhibited by the muscles 

 of the heart and vessels and by the skeletal muscles. 



The Pituitary Body. This small organ lies at the base of the 

 third ventricle of the brain with which it is connected by a short 

 hollow stalk, the infundibulum. The stalk is formed of nervous 

 tissue, and enlarges in the interior of the pituitary body becoming 

 the pons nervosa. In front of the j^ons nervosa is an epithelial 

 portion constituting the anterior lobe or pons anterior. It 

 contains numerous vessels. Between this and the pons nervosa 

 is another epithelial portion, the pons intermedium, which is only 

 slightly vascular. The pons nervosa and the pons intermedium 

 together form the posterior lobe. The pons nervosa is the least 

 vascular part of the pituitary. 



No active principle has been extracted from the anterior lobe. 

 Nevertheless there is evidence that this lobe plays an imj)ortant 



