PHYSIOLOGICAL 297 



In the familiar case of the cat molested by the dog, the increased 

 flow of adrenalin has among its numerous effects the erection of 

 the hairs on the skin, through the contraction of the minute erector 

 muscles at their base. - 



Adrenalin is chemically related to tyrosin, a common amino-acid. 

 It has been prepared synthetically. Its use in stopping nose-bleeding 

 and the like is due to its constricting action, through the sympa- 

 thetic nerve endings, on the small blood-vessels. Its potency is so 

 great that one part in a million will work. 



The use of the cortical substance of tjie suprarenal bodies is not 

 yet clear, but it appears to be essential to life. It contains in droplet- 

 form large quantities of fatty and lipoid material (cholesterol and 

 phosphatides), and many physiologists believe that it has to do 

 with the metabolism of these substances, which occur abundantly 

 in the gonads and in the central nervous system. There seems to 

 be a close correlation between the cortical substance and the 

 reproductive organs, but there is no convincing evidence of the 

 presence of a specific hormone. 



THE PITUITARY BODY.— One of .the most remarkable organs 

 in our intricate equipment is the pituitary body — far older than 

 hair, far older than fingers. It develops from an upgrowth from 

 the mouth (the oral part of the hypophysis) which meets and 

 unites with a diverticulum growing downwards from the floor of 

 the second region of the brain behind the cerebral hemispheres. 

 It is ensconced in the sella turcica of the basisphenoid, a little 

 saddle-shaped depression in one of the bones in the base of the 

 skull. Although it is a small organ, it has a complex structure, 

 and consists in mammals of four distinct parts which differ in micro- 

 scopic details. In man it is about the size of a small kidney bean. 



In the older books on anatomy and physiology the pituitary 

 body is disposed of in a few lines; and the remark is sometimes 

 made that its function is quite unknown ; for the idea of the ancients 

 that it secreted the nasal mucus or pituita is of course quite erroneous. 

 But all this neglect is a thing of the past, as may be indicated by 

 Mr. G. R. de Beer's book of over a hundred pages devoted wholly 

 to the structure and development of the pituitary body throughout 

 the Vertebrate series. A similar book might be written on the 

 functions of the pituitary body, which are not one but many. 

 The recent concentration of attention on the little organ in question 

 is due to the fact that its secretions or hormones are essential in 

 regulating or harmonising the vital functions of the body. A removal 

 of the pituitary body from an animal means cessation of growth 

 and of sexual activity, and leads to various disorders of metabolism. 



The remarkable development of the pituitary body demands 

 further description. On the one hand there is a downgrowth from 



