This line seems to mean the revulsion that triggered the vomiting was a deeply rooted revulsion, like the panic that the site of blood might cause and certainly like the emotions one would feel upon unexpectedly finding a dead person. Because of the revulsion the three turned away. Likewise the same events (the one triggering this passage, the site of blood, or finding a dead person) could trigger the nausea that produced "it." "It," of course, is the vomiting. To summarize: the event-triggering-the-passage caused two reflexes: (1) turning away and (2) nausea. The nausea produced vomiting. What I don't understand is why the three turned away from one another and not just the site. Perhaps the event was of an embarrasing nature and each of the three did want to share their reaction face-to-face.

it means that the reflex ( which means something you do without thinking) to turn away from each other while vomiting is old. they compare the reflex to the nausea ( nausea is a stomach sickness that can lead to vomiting) that made them vomit.

Hello Marissa, she is saying that the reflex and the nausea are as old as each other - ie they are both part of the human way. Hope this helps Bob