110 BLOOD-GLANDS AND DUCTLESS GLANDS. 



Nerve-fibres and small nerve-cells are abundant in the 

 medulla. 



The medullary portion of the adrenals is said to be of epi- 

 blastic origin, an outgrowth from the primitive spinal cord, 

 while the cortex is derived from the mesoblast. 



The internal secretion of the adrenals seems to be a power- 

 ful constrictor of the bloodvessels and is also probably a 

 nervous stimulant. The organ is by some regarded as a part 

 of the nervous system. 



The pituitary body (hypophysis cerebri) : The posterior lobe 

 of this body is a nervous and fibrous structure, derived from 

 and a part of the brain. The anterior lobe of the pituitary is 

 of the nature of an epithelial ductless gland, being embry- 

 onically an epithelial outgrowth from the primitive pharynx, 

 which is afterward cut off. It consists of columnar, closed 

 tubular, or rounded acini of polyhedral epithelial cells, sepa- 

 rated by fibrous septa. The acini are solid or a few may 

 possess lumina containing colloid material. Most of the cells 

 have clear bodies, but some are granular and oxyphile. 



The pituitary is supposed to produce an internal secretion 

 which has some influence on metabolism, as disease of it 

 seems to be associated with peculiar anomalies of growth 

 (acromegaly). 



The pineal body (epiphysis cerebri), a small body near the 

 corpora quadrigemina, has the structure of a ductless gland, 

 but is probably a rudimentary sense-organ. It consists of a 

 number of rounded acini lined by epithelium cells, separated 

 by and embedded in fibrous tissue. The acini contain gritty 

 particles of earthy phosphates, the " brain-sand," or " acer- 

 vulus cerebri. 7 ' 



