taking several measurements

[katdiamond1]

I've been trying to figure out this problem for a while, and I am fairly new to imagej I have this image here:


Basically what I want to be able to do is draw a line through this image, and within that line I want to get a list of all the lengths of only each white section.
Is there a function for this? Or a plugin somewhere?
I haven't been able to find it.
Thanks,
Kat