What is the most prominent feature of the machine used to pump Mildred's stomach? Why is this significant?

From the text:

"They had this machine. They had two machines, really. One of them slid down into your stomach like a black cobra down an echoing well looking for all the old water and the old time gathered there. It drank up the green matter that flowed to the top in a slow boil. Did it drink of the darkness? Did it suck out all the poisons accumulated with the years? It fed in silence with an occasional sound of inner suffocation and blind searching. It had an Eye. The impersonal operator of the machine could, by wearing a special optical helmet, gaze into the soul of the person whom he was pumping out. What did the Eye see? He did not say. He saw but did not see what the Eye saw."

There are allusions throughout 'The Hearth and the Salamander' to the intruding eye of oppression that monitors the people who live in Montag's dystopia. When the technicians pump Millie's stomach, Montag notices the tool they use looks like a writhing, mechanical one-eyed snake. The snake is the personification of evil that looks into a person's soul; it is a significant symbol of oppression.