402 THE MAINTENANCE OF THE INDIVIDUAL 



roids, adrenal medulla, and sympathetic system. It appears quite 

 conclusive, therefore, that the action of the anterior pituitary hor- 

 mone is at least partially direct. 



G. Fat Metabolism-regulating Principle. Several groups of 

 experimenters have produced evidence, since 1930, that the anterior 

 lobe of the pituitary gland also produces a hormone that regulates 

 the metabolism of fats in the body. 



H. Parathyreotropic Principle. While the evidence is not 

 irrefutable there are some grounds for believing that the control of the 

 parathyroids is made possible by a secretion from the anterior lobe of 

 the pituitary gland. 



The Intermediate Lobe 



This portion of the pituitary gland produces a hormone known as 

 intermedin, which has been found in all vertebrates so far studied. 

 The effects of this hormone may be readily demonstrated in frogs and 

 other amphibians. At the present time its function in mammals is 

 not known. 



The Posterior Lobe 



The posterior lobe of the pituitary gland consists of contributions by 

 the pars nervosa and the pars intermedia. It is possible, therefore, 

 that its products may contain secretions from both sources. Two 

 fractions have been isolated from the posterior lobe, called respectively 

 pitressin and pitocin. However, much work on these hormones still 

 remains to be done before the various effects noted on the cardio- 

 vascular, respiratory, uterine, renal organs, and the smooth muscle- 

 tissue of the intestine and mammary glands are proved to be due to 

 one or to several discrete fractions. Several characteristic reactions, 

 however, might be noted. First there is the pressor effect which is char- 

 acterized by an increased blood pressure and a decreased heart-rate. 

 Injections of the posterior lobe cause an increased secretion of urine 

 and also bring about a contraction of the plain muscle of the uterus. 

 This latter action has been made use of by the medical profession to 

 stimulate the contractions of the uterus at childbirth. If an animal 

 is lactating, injections of the posterior lobe will bring on an increased 

 flow of milk. 



From this brief account may be gathered some idea of the way in 

 which this small endocrine gland functions as the commander-in-chief 

 of the metabolism of the body. Although much work remains to be 



