A member of the “Blues” gang was rushed into an emergency room after receiving a knife wound in the left side of his thorax. The diagnosis was pneumothorax and a collapsed lung. Explain exactly (a)...

A member of the “Blues” gang was rushed into an emergency room after receiving a knife wound in the left side of his thorax. The diagnosis was pneumothorax and a collapsed lung. Explain exactly

(a) why the lung collapsed, and

(b) why only one lung (not both) collapsed.