Image map 4 is TrekkieGrrrl's vein bump/dsplc map.  Its output -the purple "cable"-  plugs into the upper socket of the math node in the bottom right corner.

     The math nodes process it and hand it off from right to left, ending with an image that has grey veins on a black background.  The last math node (bottom left) then plugs into the displacement socket and also controls the amount of blending.

• "math functions"     darkens the entire image until the background is black, with only the veins, etc remaining.
•   "mat functions 3"     is a clamp;  any pixels which are less than zero (i.e., negative) are set to zero.  I don't want any negative pixels when I take the square root.
•   "math functions 2" brightens the veins by taking the square root.  The square root of a positive number less than 1 is always greater, though still less than 1.  For example, the square root of one half is 0.7071...

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5