1098 



SUBMAMMALIAN VERTEBRATES 



TABLE 18.2 

 The relationship between anterior pituitary cells and their hormonal association in the fowl 



caudal lobe of the avian pituitary corre- 

 sponds with the entire epithelial gland of 

 the mammalian pituitary with exception of 

 the pars tuberalis. The pars tuberalis of the 

 avian and mammalian pituitary are homol- 

 ogous. A very restricted vestigial portion of 

 the mammalian epithelial gland lying near 

 the rostral end of the pituitary corresponds 

 with the cephalic lobe of the avian pituitary. 



Attempts have been made to establish the 

 relationships of some of the cells of the avian 

 pituitary with specific secretions. The tech- 

 niques used are generally the same as those 

 used for mammals (see chapter by Purves). 

 The differences in terminology used by the 

 different authors sometimes make it difficult 

 to summarize the data, but an attempt to do 

 so has been made in Table 18.2. 



In studies of these relationships castration 

 of mammals has resulted in the formation of 

 "signet-ring" cells. In the pigeon (Schooley, 

 1937), and the fowl (Payne, 1940) this does 

 not occur. However, signet-ring cells were 

 observed in young control male and female 

 chicks although never in older chicks. The 

 function of these avian signet-ring cells is 

 not known. 



Some apparent discrepancies between cy- 

 tologic evidence and hormone assays on pi- 

 tuitaries in other experiments should be 

 mentioned. Nakajo and Tanaka (1956) 



found that the bioassay of caudal and ce- 

 phalic lobes of chicken pituitaries showed 

 the presence of prolactin in both lobes. 

 The caudal lobe showed a change in potency 

 when broodiness of the hens w^as interrupted 

 by electric shock or by a strong illumination, 

 whereas the potency of the cephalic lobe re- 

 mained unchanged. If the prolactin is pro- 

 duced exclusively by the acidophils or Ai 

 cells, and if these are limited to the caudal 

 lobe, then one would not expect to find pro- 

 lactin in the cephalic lobe. Nevertheless, the 

 potency of the cephalic lobe was higher than 

 that of the caudal lobe in all bioassays re- 

 ported by Nakajo and Tanaka (1956). 



To prevent confusion in the discussion of 

 the relationship between the nervous sys- 

 tem and the pituitary, a brief description of 

 the vascularization and innervation of the 

 avian pituitary is given here. Branches of 

 the internal carotid artery supply the pitui- 

 tary. After the internal carotid artery has 

 given off the sphenomaxillaris artery and 

 the vidiana artery, the carotids bend dorso- 

 medially and enter the posterior end of the 

 sella turcica where an intercarotic anastomo- 

 ses occurs (Wingstrand, 1951; Green, 1951). 

 Near this point the inferior hypophyseal ar- 

 tery is given off to the neural lobe. After the 

 carotid arteries have separated again, sev- 

 eral arteries branch off, but only the infun- 



