Start:

Jamie: He thinks it’s consumption, doesn’t he, Papa?

Tyrone: (reluctantly) He said it might be.

Jamie: (Moved, his love for his brother coming out.) Poor kid! God damn it! (He turns on his father accusingly.) It might never have happened if you’d sent him to a real doctor when he first got sick.

[... … …]

End:

Tyrone: The less you say about Edmund’s sickness, the better for your conscience! You’re more responsible than anyone!

Jamie: (stung) That’s a lie! I won’t stand for that, Papa!

For full extended scene, please refer to clips or the script edition cited here: Eugene O’Neill, Long Day’s Journey Into Night, Yale Books, 2002, pp. 30-35.