ANATOMY OF THE POISON GLAND OF HELODERMA. 



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In its general structure each lobe may be described as a compound tubular 

 gland. The axis of the gland is formed by the common lumen of the collecting 

 and excretory ducts. From this lumen at all levels are given off numerous 

 smaller tubules, the intralobular tubules, which, branching repeatedly, radiate 

 toward the periphery of the containing lobule to form the terminal acini. 

 Topographically there is no sharp distinction between the terminal acini and 

 the intralobular tubules; both are perfectly continuous, show approximately 

 the same diameter throughout, and contain a wide and clear lumen. This 

 lumen is always open; it is never obscured by the surrounding cells, even when 

 the latter are swollen with the secretions (figs. 7, 9, and 12). 



Fig. 8. — Outline drawing of a section of poison gland, showing three lobules. Drawing was made to show arrange- 

 ment of inter- and intralobular .septa and distribution of granule-secreting cells; the latter indicated by 

 dotted portions of the epithelium of the tubules. The epithelium is merely outlined, none of the constit- 

 uents, excepting the granules, being shown (Zeiss oc. 4, obj. 8 mm.). 



In any lobule of considerable size there may be distinguished two regions: 

 (a) a peripheral zone formed of more or less clearly defined clusters of terminal 

 acini and (6) a central area composed of intralobular tubules. The latter con- 

 verge from the periphery toward the center of the lobule and there unite to form 

 a few central tubules which open into the large collecting duct (figs. 7 and 8) . 



We shall now consider in order the structure of the cells in (1) the central 

 collecting duct, (2) the intralobular tubules, and (3) the terminal acini. In 

 each of these parts, as previously noted by Holm, the cells are characteristic. 



