Eliminating a level in a structure or table

I have participant data that I would like to reoganize after some processing. For each participant, there are multiple visits, then multiple timeseries of data for each visit. I need to do some processing of the data separately for each day first (hence the reason for importing the data this way), but then would like to concatinate the processed data, eliminating the "day" level. Basically my data starts in a structure like this:

Kid(x).Visit(y).Fields

There are about x=40 different Kids, with y=up to 4 visits per kid and the same fields in each (though not the same length, times and numeric vectors). I would like to concatinate to

Kid.Fields (where fields contains all the data from Visit(1) though Visit(4). Seems like this should be relatively simple, but I can't figure it out.

Thanks!

[Walter Roberson]

[Kids(x).Visit.Fields]