COORDINATION 



447 



wide variety of diseases, some biologists 

 believe that we have an entirely new ap- 

 proach to the study of organic disease. 

 However, it is too early to draw any conclu- 

 sions from these observations. 



The pituitary 



The last and perhaps the most complex 

 of all the endocrine glands is the pituitary, 

 or hypophysis. Located in approximately 

 the middle of the head, it lies in a bony 

 capsule and is attached to the base of the 

 brain by a slender stalk, the infundibulum 

 ( Fig. 16-34 ) . Like the adrenals, the hypoph- 

 ysis is a double gland, composed of two 

 principal lobes: the anterior, which arises 

 embryologically from an outpocketing of 

 the roof of the pharynx; and the posterior, 

 which originates as a solid outgrowth from 

 the floor of the brain. The point of contact 

 with the brain through the infundibulum 

 is retained while all connections with the 

 pharynx are lost very early in embryologi- 

 cal development. The anterior lobe is the 

 larger of the two, although the entire hu- 

 man pituitary would compare favorably in 

 size with a large pea. Because of its incon- 

 venient location and complexity research 

 has been arduous and relatively slow, al- 

 tliough very recently interest has been 

 renewed through the discovery of some 

 new, therapeutically important, extracts. 

 Although it is very difficult to operate on 

 the pituitary in man, experimental animals 

 such as the frog and rat lend themselves to 

 such surgery. By perforating the roof of 

 the mouth the pituitary can be neatly re- 

 moved and subsequent effects observed. 

 When this operation is performed on a 

 young mammal, growth is inhibited at 

 once, sexual maturity never occurs, and 

 both the thyroid and the adrenal cortex 

 atrophy. With the injection of pituitary ex- 

 tracts, the animal develops normally and 

 the associated symptoms never appear. 

 From these observations it is clear that the 

 pituitary certainly gives rise to more than 



Fig. 16-35. Case of giantism. The men on either side are 

 of normal height. 



one hormone and that its influence is far- 

 reaching in the animal body. 



The anterior lobe. Five well-known hor- 

 mones are produced by this lobe, and there 

 may be others. The five are named accord- 

 ing to the part of the body that they affect, 

 with the addition of the suffix trophin: 

 somatotrophin (growth), thyrototrophin 

 (thyroid), corticotrophin (adrenal cor- 

 tex), gonadotrophin (gonads) and mam- 

 motrophin (mammary). Each of these will 

 be considered briefly in this order. 



Somatotrophin effects. The function of 

 the pituitary was brought to the attention 

 of early anatomists by the fact that an en- 

 larged gland was always associated with 

 giantism. These huge men (Goliath, whom 

 David slew, was undoubtedly one) reach 

 a height of nearly 9 feet and are rather well 

 proportioned, with the exception of the ex- 

 tremities which are longer than normal. 

 (Fig. 16-35). An examination of the an- 



