10 



perforated by small holes, and consist of a thin layer of 

 connective tissue covered on either side by the secretory 

 columnar epithelium. An oblique diaphragm limits the 

 region of the gland, and is perforated by a hole for the 

 passage of the ink. At the base of the gland is found a 

 whitish mass of round non-glandular cells (fig. 26, gldj. 

 This is the formative region where the trabeculae 

 originate. The initially indifferent cells become differen- 

 tiated into either the connective tissue or the secretory 

 cells of the trabeculae. These trabeculae are constantly 

 being formed and travelling forwards to the anterior end 

 of the glandular region. Tracing their course and 

 structure as they go, it is found that the young cells 

 gradually accumulate pigment granules, and when they 

 are full burst. Thus the ink is freed and the secretory 

 cells destroyed. Towards the anterior end of the gland, 

 then, the trabeculae disintegrate, and are constantly 

 replaced by the younger ones behind (Clirod). The 

 secretion is a thick dark-brown liquid, and a few drops 

 will colour a large volume of water. On drying, a dark- 

 brown powder is obtained. The liquid consists of a 

 colourless transparent plasma, having minute dark- 

 brown pigment granules in suspension. On analysis it 

 is found to contain both copper and iron, extracted from 

 the blood (Grirod), Although the actual secretion of the 

 ink is continuous, its passage to the exterior is 

 intermittent and voluntary. After expulsion from the 

 anus, the ink is discharged, along with a jet of water, 

 through the funnel. 



