HEART AUSCULTATION (where to listen with stethoscope):
Best heard on LEFT side, low chest, in the cardiac region (3rd-5th intercostal space):
- Pulmonary valve — Left, 3rd ICS, low (P-T-A-M from front to back, low to high).
- Aortic valve — Left, 4th ICS, higher.
- Mitral (Left AV) — Left, 4th-5th ICS, low.
- Tricuspid (Right AV) — RIGHT, 3rd-4th ICS, low.

LUNG AUSCULTATION FIELD (Triangle):
Boundaries:
- Cranial: caudal border of triceps muscle (approx. 5th rib).
- Dorsal: lateral edge of epaxial muscles (under the spine).
- Caudo-ventral: line of pleural reflection (8th costochondral junction → 11th rib → 13th rib head).

PERCUSSION FIELD: Same triangle. Normal lung = resonant. Dull = fluid/consolidation. Hyper-resonant = air (pneumothorax).

PARACENTESIS THORACIS (Thoracocentesis):
Site: 7th or 8th intercostal space, low on chest wall, just above the costochondral junction, on the CRANIAL border of the rib (avoid V-A-N in costal groove of the rib in front).
Use: To drain pleural effusion, blood or air; to take fluid sample.

CLINICAL EXAMINATION OF THE THORAX

1. AUSCULTATION OF THE HEART (using a stethoscope)
The heart is best heard on the LEFT side of the chest, low down (between elbow and sternum), behind a 'window' of the triceps mass (the muscle of the upper arm covers the cranial part of the heart).

Valve listening points (P-T-A-M order from cranial to caudal on the LEFT side):
• P — Pulmonary valve: Left side, 3rd intercostal space (ICS), low on chest.
• A — Aortic valve: Left side, 4th ICS, slightly higher than pulmonary.
• M — Mitral (Left AV) valve: Left side, 4th-5th ICS, low — this is where the loudest 'lub-dub' is normally heard.
• T — Tricuspid (Right AV) valve: RIGHT side of chest, 3rd-4th ICS, low.

Heart sounds:
• S1 ('lub') = closure of AV valves (start of systole).
• S2 ('dub') = closure of semilunar valves (start of diastole).
Murmurs (whooshing sounds) suggest valve disease.

2. AUSCULTATION & PERCUSSION OF LUNGS — the 'TRIANGLE'
The area where lung sounds can be heard/percussed is bounded by:
• Cranial border: The caudal border of the triceps muscle (approximately the 5th rib).
• Dorsal border: A horizontal line at the lateral edge of the epaxial (back) muscles, just below the transverse processes.
• Caudo-ventral border (slanting line): Follows the line of pleural reflection.
– In OX: from 8th costochondral junction → middle of 11th rib → head of 13th rib.
– In HORSE: 6th-11th-17th rib (curved line).
– In DOG: 6th-9th-11th rib.

Inside this triangle: normal vesicular ('breezy') sounds.
• Crackles/rales = popping sounds → fluid in alveoli (pneumonia, pulmonary oedema).
• Wheezes/rhonchi = whistling → airway narrowing (asthma, bronchitis).
• Pleural friction rub = rough rubbing → pleurisy.

Percussion (tapping the chest):
• Resonant note — normal air-filled lung.
• Dull note — fluid (pleural effusion) or solid (consolidation in pneumonia).
• Hyper-resonant (tympanic) note — air outside lung (pneumothorax).

3. PARACENTESIS THORACIS (THORACOCENTESIS)
This is the puncture of the chest wall to remove fluid or air from the pleural cavity.

SITE (in ox):
• Usually 7th or 8th intercostal space, on the LEFT side (to avoid the heart base on the right).
• Low on the chest wall — just above the costochondral junction (because fluid settles low when animal is standing).
• Always insert the needle along the CRANIAL border of the caudal rib (to avoid the intercostal vein-artery-nerve which lie in the costal groove on the caudal border of the rib in front).

USES:
• Diagnostic — to obtain a sample of pleural fluid (cytology, culture).
• Therapeutic — to drain pleural effusion or air (pneumothorax).

PRECAUTIONS:
• Use sterile technique.
• Insert with bevel up; advance slowly until you feel the 'pop' through the parietal pleura.
• Avoid going too deep (lung puncture).
• In horse/dog, since mediastinum is fenestrated, you may drain both sides through one puncture; in ox, both sides usually need separate punctures.