44 SOURCES OF KINETIC AND METABOLIC HORMONES 



Table 4. Cells in the pars distalis of the adenohypophysis 



* See glossary. 



t PAS = Periodic acid-Schiff method, with which these cells give a 

 positive reaction. 



no iodine. This region is well known to secrete a melanophore 

 dispersing hormone, intermedin, in many fish and most amphi- 

 bians, but not in Agnatha. It has also been claimed that this lobe 

 may act as a storage-and-release centre for adrenocorticotrophin, 

 ACTH (Mialhe-Voloss, 1955). The claim may be due to the 

 chemical identity of intermedin with a large part of the chain 

 molecule that makes up ACTH. 



2.2 Endodermal sources in Vertebrata 

 Hormones secreted from endodermal sources have so far only 

 been recognized in vertebrates. They fall into two categories: 

 isolated cells in the stomach and intestinal mucosa (§ 2.21) and 

 well-developed endocrine glands in the pharynx and pancreas 

 (§ 2.22). The former secrete kinetic hormones which control gut 

 muscles and the secretion of digestive enzymes from exocrine 

 glands ; the latter secrete various metabolic hormones (Table 5). 



2.21 ISOLATED CELLS IN THE GUT 



A large number of hormones can be located in the stomach and 

 intestine of mammals ; some of these also occur in birds, but they 

 are not known to be active in cold-blooded vertebrates. 



