Like so much of the diction in this chapter the phrase can be read in two
senses: first, as laughter without cause, as though Victor's heart is not
in it; second, as a cold, self-obsessed, or unfeeling discharge of
nervous energy. Although the first meaning is the natural way to
construe the diction, the second remains behind, like a sour aftertaste,
to affect our later judgments. It is allied to the intimation of madness
expressed by the wildness of Victor's eyes.