SECRETION OF THE DUCTLESS GLANDS. 



881 



In the pars nervosa characteristic hyaline or colloid bodies 

 occur and histological work makes it probable that this material 

 constitutes an internal secretion. According to Herring,* it is 

 formed from the epithelium of the pars intermedia. The cells of 

 the latter invade the pars nervosa, undergo a hyaline degeneration, 

 and are finally discharged into the cerebrospinal liquid of the third 

 ventricle. Investigations upon the physiology of the pituitary 

 gland have taken the two usual directions, namely, a study of the 

 effects of removal and a study of the effects of extracts, and obser- 



, 



Fig. 299. Median sagittal section through pituitary of monkey; semidiagrammatic 

 (Herring): a, Optic chiasma; b, third ventricle; c, g, pars intermedia; d, epithelium of pars 

 intermedia extending round neck of pars nervosa; e, pars glandularis seu epithelialis; /, intra- 

 glandular cleft, lying between pars glandularis (e) and pars intermedia (g) ; h, pars nervosa. 



vations of this character have been made upon this gland as a 

 whole and upon the anterior and posterior lobes taken separately. 

 Extracts of the Posterior Lobe. Extracts of this lobe contain ma- 

 terial from both the pars nervosa and the pars intermedia, but on 

 the evidence stated above it may be assumed that the results ob- 

 tained are attributable in reality to the pars intermedia, which has 

 a glandular structure and is responsible for the hyaline material 

 found in the nervous part. When extracts of the posterior lobe 

 are injected into the circulation several distinct results have been 

 observed to follow. In the first place there is a characteristic effect 



* Herring, "Quarterly Journal of Experimental Physiology," 1, 121, 161, 

 281, 1908. 

 56 



