Sentence:  Were the larynx of the little creature like that of the parent, the milk might—probably would—enter the windpipe and cause suffocation : but the fœtal larynx is cone-shaped, with the opening at the apex, which projects, as in the whale-tribe, into the back <WSD>aperture</WSD> of the nostrils, where it is closely embraced by muscles of the ‘soft palate.' 
Meaning of the word marked with <WSD> tags:  An opening, gap, or hole, usually small and narrow