Calculating Cumulative Area of Heterogenous Particles

[blarz15]

Hi,

I am using ImageJ Version 1.43c, and I would like to compute the cumulative area of heterogenous particles in images such as these:






From reading previous posts, I understand that I will first need to use the Threshold feature to eliminate the background.  However, I am having some difficulty getting this function to work properly.  For example, when I attempt to threshold the image shown above, this is what I get:



Moving the threshold min/max scroll bar does not appear to effect the image, and I am therefore unable to subtract the background.  What am I doing wrong?

Assuming that I could somehow get the background subtracted, how would I then calculate the cumulative area of all the remaining particles in the field?  I don't need units in my area calculation, because I will simply be comparing the relative areas between many images.    

Any advice would be GREATLY appreciated!  

Thanks so much,

Barrett