ENDOCRINE GLANDS AND THEIR FUNCTIONS 199 



bones and for deficient formation of enamel and dentine of the teeth. 

 Calcium is needed for both the teeth and the bones and the introduc- 

 tion of either calcium or parathormone into the body is made to sup- 

 plement a deficient supply of calcium due to malfunctioning of the 

 parathyroids. Removal of the parathyroids also brings about a fall 

 in the renal excretion of phosphorus, and the injection of parathor- 

 mone causes an immediate rise in the level of renal phosphorus. 

 Parathyroid activity is particularly useful to laying hens where so 

 much calcium is needed in shell formation. There is evidence of a 

 close functional relationship between the pituitary gland and the 

 parathyroid. In dogs the removal of the pituitary causes atrophy of 

 the parathyroids, particularly if the pancreas has been removed also. 

 Conversely it has been noticed that injections of extract from an- 

 terior pituitary raises blood calcium in some species because of in- 

 creased activity of the parathyroids. 



Too great an activity on the part of the parathyroid glands results 

 in a decalcification of the bones, and an increased content of calcium 

 in the blood and in the excretion of the kidneys. The final result of 

 this softening of the bones may cause serious disfiguration and stunt- 

 ing of the body. Accompanying these results are flabbiness of the 

 muscles, decreased irritability of the nervous system, and other un- 

 favorable conditions. These may be remedied by the removal of a 

 portion of the parathyroids. 



The Suprarenal Bodies 



Lying close to and slightly anterior to the kidneys are two small yel- 

 low or reddish masses of tissue, which play a prominent role in the 

 regulation of the body and one of such complexity that much is yet 

 to be learned concerning its method of functioning. These adrenal 

 glands, or suprarenal bodies, are made up of an inner and an outer 

 portion, the medulla and cortex respectively. The former secretes a 

 substance designated as adrenalin (epinephrine or adrenin), which 

 acts upon various organs and raises the level of their functioning. 

 Adrenalin, at times of excitement or emergency, may cause con- 

 striction of blood vessels, increased rate of heartbeat, a greater 

 discharge of glucose from the liver to provide additional energy, 

 erection of hairs, stimulation or inhibition of the various visceral 

 muscles, etc., to provide greater efficiency. The range of control of 

 the medullary portion of the adrenals is thus wide and complex, 

 definitely interrelated with the functions of the sympathetic nervous 



