XI] ORGANS OF INTERNAL SECRETION 147 



part in metabolism. Thus tumours growing on the anterior 

 lobe are often associated with acromegalj" (or overgrowth of the 

 bones of the face) and gigantism (or overgrowth of the bones of 

 the limbs, the epiph^-ses not ossifying). These diseases are 

 thought to be the result of hyperpituitarism. On the other hand 

 pituitary tumours may produce an atrophy of the gland and so 

 be a cause of h3'popituitarism. 



Active extracts containing hormones have been obtained 

 from the posterior lobe. Thus Ho\\ell found that there was 

 a hormone which acted on the heart and vessels, causing a 

 great rise of blood pressure, strengthening the heart beats and 

 constricting the arteries. Schafer and Herring found that 

 posterior lobe extract has a diuretic effect on the kidneys ; Weed 

 and Gushing ascertained that the extract has a stimulating action 

 on the flow of the fluid of the cerebro-spinal canal ; and Ott antl 

 Scott discovered the galactogogue effect of extract of posterior 

 lobe (see p. 198). It would ajopear therefore that the pituitary 

 produces several hormones each having its characteristic function, 

 but none of these have been isolated. 



The Pineal Body. This is a very small glandular organ 

 situated on the dorsal surface of the third ventricle. Its functions 

 have not been ascertained, but it has been found that injection 

 of pineal extract has a slight galactogogue action. 



The internal secretions of the generative glands are more 

 conveniently treated of in the chapters dealing with these organs. 



The Inter-Relation of the Organs of Internal Secretion. 

 There is considerable evidence of a functional inter-relation 

 of certain of the organs of internal secretion with one 

 another, but the whole subject is very obscure. It has been 

 ascertained that removal of the th3'roid leads to hj'pertrophy of 

 the pituitarj^, but it is not very apparent whether the growth is 

 compensatory or whether the two organs are antagonistic. 

 Colloid substances tend to arise in the jDons anterior of the 

 pituitary after thyroidectomy, and there is an increased activity 

 in other portions of the gland. There is also some relation 

 between the suprarenals and thyroids since thyroid secretion 

 appears to promote suprarenal activity, while thjToidectomy 

 diminishes the secretion of the suprarenals. Again, extracts of 

 suprarenal medulla and pituitary posterior lobe seem mutualh' 

 to facilitate each other's action on the vessels. The connection 



