22 



THE VENOM OF HELODERMA. 



As already mentioned in the section on the gross anatomy, the entire 

 poison gland is invested by a continuous capsule of fibrous tissue. From this 

 several relatively thick septa extend inward, completely dividing the gland 

 into three or four entirely independent parts or lobes. Each lobe is a pear- 

 shaped sac. The center of the lobe is occupied by a relatively capacious 

 lumen, which I shall term the central collecting duct. At its upper end this 

 narrows gradually to form the excretory duct, which opens at the apex of the 

 lobe. The walls of the sac are thick and formed chiefly of glandular tissue. 

 From these walls minute intralobular tubules open into the collecting duct. 



FIG. 7. Part of section of normal poison gland, showing typical histological structure (Zeiss oc. 4, obj. 8 mm.). 



Each lobe is subdivided into a large number of lobules by septa which are 

 given off from the investing capsule and the fibrous partitions separating the 

 lobes. These septa extend through the gland tissue as far as the central col- 

 lecting duct (figs. 7 and 8). Each lobule is further cut into several smaller 

 lobules by secondary septa which interpenetrate it in all directions, and this 

 subdivision continues until the terminal acini are reached, each of which is 

 separated from its neighbors by a delicate septum (figs. 7, 8, and 9). 



