ANATOMY, UNSOUNDNESS, AND AGE OF A HORSE 39 



Respiratory system.— This consists of the nostrils, 

 pharynx, larynx, trachial tubes and lungs. The lungs are 

 the central organs and are two in number. They consist 

 of a great number of small sacs, which are collected into 

 lobes of various sizes, each of which is connected with the 



FIG. 21.— RESPIRATORY SYSTEM 



1. Cranial cavity 



2. Guttural pouch 



3. Nasal cavity 



4. Tongue 



5. Pharyngeal cavity 



6. Cavity of larynx 



7. Epiglottis 



8. Trachea 



9. Oesophagus 



10. Left bronchus 



1 1. Right bronchus 



12. Right lung 



13. Left lung 



14. Sternum 



15. Ribs 



16. Heart 



17. Posterior aorta 

 IS. Anterior aorta 



branches of the bronchial tubes. It is by means of these 

 lobes and sacs that the lungs relieve the blood of its waste 

 materials and invest it with a fresh supply of oxygen 

 during respiration. (Fig. 21.) 



Digestive system. — This apparatus consists of a series 

 of organs which receive and digest the food. These 

 organs are the mouth, pharynx, oesophagus, stomach and 

 intestines. The stomach of the horse is a single organ 

 and is much smaller than the stomach of the cow, having 



