174 W. p. R. WELDON. 



The tubules are for the most part aggregated into con- 

 siderable lobuli ; but here and there these lobuli become 

 smaller, and in some sections tubules are seen which project 

 separately into the pericardium ; several such were cut trans- 

 versely in the section from which fig. 3 was drawn, and they 

 are seen to be separately invested by pericardium. 



Passing inwards towards the centre of the gland, the tubules 

 unite with one another, still maintaining the same characters, 

 and not showing any appreciable change in diameter, till they 

 finally open into a large central duct (fig. 3, c. d.). 



The central duct is elliptical in cross section, its long diameter 

 being about 0*2 mm., its short diameter 05 mm. ; it may be 

 single, as represented in the diagrammatic longitudinal section 

 (fig. 2), or it may be divided into two or three anastomosing 

 branches. It is lined by a single layer of very long and slender 

 columnar cells, each about 007 mm. long by about 0*009 mm. 

 broad, and having a large oval nucleus, with a dark outline and 

 granular contents towards its outer end. The protoplasm of 

 these cells is crowded with granules (fig. 4), and the free ex- 

 tremity of each is produced into a number of fine pseudopodia, 

 round which are collected numerous granules (fig. 4). It is 

 difficult to avoid the belief that the appearances described are 

 due to the fact of the epithelium cells being actively amoeboid 

 during life, and of their pouring into the lumen of the central 

 duct a quantity of secretion granules. 



Outside this epithelium is a strong basement membrane 

 (figs. 4, Q, m), which is connected with a tolerably compact 

 coating of connective tissue, investing the whole duct. 



The lumen of the duct v;as filled, in all my preparations, 

 with a larger or smaller amount of material resembling a blood- 

 clot, and consisting of a finely granular matrix (fig. 5), in which 

 were contained oval nucleated cells, identical, so far as I was 

 able to see, with the red blood-corpuscles found in blood-clots 

 from the surrounding vessels. After a careful comparison, both 

 with sections and with teased- out preparations of the blood- 

 clots of the great veins, I have been unable to come to any 

 other conclusion than that the central duct does actually con- 



