THE PARAGAXCWJA 415 



diverticulum from the floor of the third ventricle. The remains of 

 the diverticulum constitute the infundibulum. 



The so-called middle lobe or pars intermedia is a thin layer of tissue 

 which covers the anterior aspect of the posterior lobe thus lying 

 between it and the interglandular cleft. It develops with the anterior 

 lobe and like it consists of a connective-tissue framework and epithe- 

 lial cells. It is less vascular, however, and its cells are smaller 

 and less distinctly granular. The cells lining the cleft are columnar, 

 thus contrasting with the flat cells of the opposite wall. Character- 

 istic of the pars intermedia are small cyst-like structures which con- 

 tain colloid, presenting an appearance not wholly unlike thyreoid, 

 although chemical!}- the colloid cf the two glands is not identical. 

 Lining these tiny cysts is a cuboidal epithelium. 



The nature of ihe secretion, its function, and its relation to the various kinds 

 of cells have been subjects of much controversy. The granules within the cells 

 undoubtedly represent an intracellular stage of the secretion. According to 

 some investigators each type of cell contributes its own special secretion to the 

 general secretion of the gland. According to most authorities the different 

 types of cells represent merely different stages in the elaboration of the secretion. 

 Some consider the colloid a special secretion, others derive it from the cell 

 granules and consider it as possibly representing a final stage, or "normal de- 

 generative condition of the secretion." 



Pregnancy apparently induces increased activity of the gland. This is of 

 interest in connection with the clinical use of the extract of pituitary body for 

 the purpose of inducing contractions in an atonic uterus during parturition or 

 for the control of post-partum bleeding. Pathological conditions of the pitu- 

 itary, more particularly tumors or hyperplasia of the anterior lobe, are apparently 

 associated with a clinical condition known as acromegal}^ in which there is 

 marked connective-tissue hypertrophy, especially of certain bones. The con- 

 nection between acromegaly and lesions of the pituitary body would seem to be 

 somewhat similar to that between myxcedema and lesions of the thyreoid. Re- 

 moval of the thyreoid results in enlargement of the pituitary body, especially 

 in increase of colloid. Increase of colloid has also been reported after removal 

 of the pancreas. 



The Paraganglia 



Under the head of ParagangHa are grouped certain small ductless 

 glands and small groups of cells which are closely associated both 

 anatomically and embryologically with the sympathetic system. 

 They include the carotid, the coccygeal, and tympanic glands, the para- 

 sympathetic organ of Zuckerkandl, and the medulla of the adrenals. 

 The most marked characteristic of these organs aside from their 



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