CH. VII] 



SNAILS AND SLUGS 



221 



extent deprived of oxygen, is conveyed to the pulmonary 

 sinus. This is a large sinus running a nearly circular 

 course round the base of the pulmonary chamber and 

 receiving many small veins from the rectum. From the 

 pulmonary sinus the blood is distributed through smaller 



Fig. 42. Helix pomatia, with the upper wall of the pulmonary chamber 

 cut open and folded back. From Hatschek and Cori. 



1. Ventricle. 2. Anterior tentacles. 3. Eye tentacles. 4. Cut 

 edge of mantle. 5. Eespiratory pore. 6. Anus. 7. Opening 

 of ureter. 8. Foot. 9. Auricle receiving pulmonary vein. 



10. Rectum. 11. Nephridium. 12. Upper wall of pulmonary 

 chamber. 



