EXPLANATIONS. 393 



6. Mitral valve. 



15, 7, 24. The right auricular region. 



8. Base of the left auricle. 



10, 10. Division of the valves on the left side of the heart. 



12. The vena cava, which empties the venous blood into the right 

 auricle. 



13. Carnae columnse, or fleshy pillars within the right ventricle. 



14. A portion of the tricuspid valve. 



15. The region of the left auricle. 



16. 16. Pulmonary veins, which return the blood from the lungs to the 

 left auricle. 



17. Great aorta. 



19. A probe inserted into one of the pulmonary veins. (The lower 

 end of the probe should be seen at 6, but the artist has failed to show it.) 



20. A probe inserted into one of the pulmonary arteries ; the other ar- 

 tery is in close contact with the former : they both carry blood to the 

 lungs for oxygenation. 



22, which is seen under 14, is the tendinous cords of the right ventricle. 



22, 22, 22, are the transverse bands running across the ventricles. 



23, 23, 23. The tendinous cords of the left ventricle. 



24. Base of the right auricle. 



25. A portion of the os cordis, or bone of the heart. 



STRUCTURE OF THE HEAD AND HORNS. 



1 . The osseous, or bony structure of horn. 



2. The frontal bone. 



3. 3. The frontal sinus, which extends from the bones of the nose 

 nearly up to the tip of the horn. 



4. The round, or condyloid process, and the region where the spinal 

 marrow passes from the skull. 



5. The cranial cavity in which the brwn is lodged. 

 6.' A portion of the temporal bone. 



7. Inlet to the ear. 



8. Internal surface of the cheek bone. • 

 13, 14. Portion of the aethmoid and sphenoid bones. 



18. The aethmoid bone. 



19. Turbinated bone 



