首楞嚴義疏注經 3.76

3.76

集，聚也。中，猶內也。吸、撮，皆取也。由生滅境引發集聚內覺知性，此之覺知常取生滅，於內分別，非同前五照外境界，故名內塵，以意根內緣不緣外故，即前文中聚緣內搖也。

'Gathers' means collects. 'Within' is like the interior. 'Inhaling' and 'seizing' both mean grasping. Due to the objects of arising and cessation, the internal aware and knowing nature is brought forth and gathered; this awareness and knowing constantly grasps arising and cessation, discriminating internally, unlike the previous five which illuminate external sense objects; therefore they are called 'internal dusts', because the mind faculty conditions internally and does not condition externally, which is the 'gathering of conditions wavering within' in the preceding text.