THE PITUITARY 241 



occurring usually within forty-eight hours. When the 

 animal is moribund, stimulation of vaso-constrictor fibres 

 is without effect upon the blood-vessels. 



Administration of suprarenal extract, whether to patients 

 suffering from Addison's disease or to animals from which 

 the glands have been removed, at most only prolongs 

 hfe slightly. 



It is clear that the function of the medulla is to produce 

 adrenahn. The part which adrenahn plays in the animal 

 economy, hke the part which the sympathetic nerves play, 

 is to adapt the animal to efforts of defence or offence in 

 emergency. The quickened heart-beat, the varied blood- 

 pressure, the intestinal paralysis, the relaxation of the 

 branchioles, the secretion of sweat, the mobilisation of 

 sugar, are all means to this end. 



THE PITUITARY BODY 



Structure 



The pituitary body is composed of three parts, which 

 are histologically distinct. 



The Pars Anterior consists of a mass of epithelial cells, 

 some of which contain basophile granules, some oxyphile 

 granules. In others the protoplasm is clear. These cells 

 abut on large blood-sinuses. The pars anterior is incom- 

 pletely separated by a narrow cleft from the 



Pars Intermedia. — Although continuous with the pars 

 anterior at the circumference of the cleft, the pars inter- 

 media differs in certain respects from the pars anterior. 

 It is less vascular; the cells contain neutrophile granules, 

 and are here and there disposed in vesicles which contain 

 colloid. The pars intermedia is closely adherent to the 



Pars Posterior {or Nervosa). — This consists of neuroglial 

 fibres and cells and has only a scanty blood supply. Appear- 

 ances have been described which suggest that the colloid 

 material secreted bv the pars intermedia passes into the 

 16 



