"Sea and headland now grew dim. Pulses were beating in his eyes, veiling their sight, and he felt the fever of his cheeks." The American idiom “seeing red” probably comes from the experience of having adrenaline-charged blood rush through vessels in the eyeball. Intense anger can also produce a "fever" of blood in the cheeks, similar to the blush of embarrassment that has just suffused Mulligan's cheeks when confronted with his harsh words about Stephen and his mother's death: "A flush which made him seem younger and more engaging rose to Buck Mulligan's cheek."
But Stephen's physical passion is rooted in more depth of feeling and more understanding of personal dynamics. Mulligan is aware only of having committed a social impropriety: "I didn't mean to offend the memory of your mother." Stephen is angry because of something else, "the offence to me" created by his friend's callous indifference to his suffering.
Mulligan defends himself at length against what he thinks to be Stephen's anger at hearing his mother described as “beastly dead.” But between two freethinking men such a description should not be particularly disturbing; indeed, it is easy to imagine that someone raging at the loss of a loved one would sympathize with such a blunt statement. Saying “it’s only Dedalus,” however, is virtually certain to wound and antagonize. A person wrestling with grief feels acute narcissistic self-absorption: the foundations of life have collapsed, and yet the world somehow goes on all around, unconsciously, cruelly. To have one’s importance callously dismissed in such a state is maddening. Mulligan does it to an ostensibly close friend. He cannot understand why Stephen's feelings would be hurt, and he compounds the injury by going on the offensive and exploiting Stephen's guilt about how he treated his mother. All these actions betray a breathtaking unconsciousness and indifference.
In the schemas which Joyce gave to Carlo Linati and Valery Larbaud, a bodily organ is associated with each episode of the book, with the exception of Stephen's chapters: Telemachus, Nestor, Proteus. The usual interpretation of this omission (almost certainly valid) is that Stephen, unlike Bloom, lives almost entirely in his head, and not in his body. There are limits to the validity of the insight, however. The pulses in Stephen's eyes, the fever in his cheeks, and "the gaping wounds" that Mulligan's words tear in his heart, show a man who, at this moment at least, is living very intensely and unhappily in his body. Mulligan, for all his athletic, hedonistic wellbeing, does not have a clue about the grief, love, and sympathy that a healthily embodied person feels.