They were large nostrils, tokening his descent from savage ancestors who had survived by virtue of deep lungs and generous air-passages.

Exhaling or inhaling, their air-passages had snapped shut as that dread "Vee-Two" was heard, and they had literally jumped into their armored suits of space - flushing them out with volume after volume of unquestionable air; holding their breath to the last possible second, until their straining lungs could endure no more.