SECRETION. 317 



When the heart is freed from nervous control its contractions are in- 

 creased both in force and frequency, still further raising blood-pressure. 

 The contraction of the skeletal muscles in response to a single stimulus 

 is much prolonged. 



Very small doses of supra-renal extract are sufficient to produce 

 marked effects. Thus Schafer states that less than -rrinnj- gramme (-g-^g- 

 grain) of the desiccated gland is sufficient to produce an effect upon the 

 heart and arteries of an adult man. 



It is a curious fact that only extracts of the medullary portion of the 

 gland are active. 



Abel has succeeded in separating the blood-pressure-raising constitu- 

 ent of the extract, and calls it epinephrin. By nature it is related to 

 the alkaloid group. 



Destruction of the supra-renal capsules through disease in man re- 

 sults in the production of a group of symptoms known as Addison's dis- 

 ease. The administration of supra-renal extract to these cases sometimes 

 results beneficially, but not so uniformly as thyroid feeding does in myx- 

 cedema. Yet Langlois states that if one-sixth of the supra-renal capsule 

 by weight be left in the dog, the animal survives the operation of re- 

 moval. 



On the whole, the assumption that the supra-renal capsules produce 

 an internal secretion which is essential to life is warranted. 



The Pituitary Body. This body is a small reddish-gray mass, 

 occupying the sella turcica of the sphenoid bone. 



Structure. It consists of two lobes a small posterior one, consist- 

 ing of nervous tissue; an anterior larger one, resembling the thyroid in 

 structure. A canal lined with flattened or with ciliated epithelium 

 passes through the anterior lobe; it is connected with the infnndib- 

 ulum. The gland spaces are oval, nearly round at the periphery, 

 spherical toward the centre of the organ ; they are filled with nucleated 

 cells of various sizes and shapes not unlike ganglion cells, collected to- 

 gether into rounded masses, filling the vesicles, and contained in a semi- 

 fluid granular substance. The vesicles are inclosed by connective tissue 

 rich in capillaries. 



Function. The function of the pituitary body has not yet been es- 

 tablished. Some observers have found that its removal causes death, 

 preceded by symptoms resembling those of thyroid removal. Hence it 

 has been supposed that the pituitary body has a function identical with 

 or analogous to that of the thyroid. On the other hand, tumors or 

 other disease of the pituitary body have been found after death in asso- 

 ciation with a disease known as acromegaly, in which the bones and soft 

 parts undergo great hypertrophy. In this connection it must be remem- 

 bered that the two lobes of the pituitary body are morphologically and 

 embryologically distinct. 



