Thazriah - Metzorah: Signs, symptoms, semiotics

At first,  it seems quite strange.  These untranslatable words, relating to skin lesions.  White spots that appear deep, below the surface; red and green spots on cloth, on houses.  The signs of tzorath, a disorder translated as leprosy by the King James Committee. 

The problem is the consequences.  Having these signs means a brief imprisonment.  Do the spots spread? Do they fade? Do they remain?   And if the wrong thing happens, the object -  the cloth or the house - is destroyed.  And of it is a person - he is isolated from the camp, she must cover all of her body and announce his contamination. 

To an oncologist, this is not so strange.  A swollen lymph node on the left shoulder points to malignancy in the abdomen.   A black spot  on an arm with a swollen gland in the armpit means that the angel of death is lurking. A bloody nose in an Ebola area warns of contagion.  We call this science.  We can show the connections, aided by Google images.  The idea that certain signs, in themselves trivial,  indicate  a significant issue was the basis of the medical diagnostic mystique.  The interpretation of these signs made doctors  appear prophetic - from Hippocrates to Dr. Zorba to House. 

We have lost the circuit diagram. The connection between spots and tahara ( purity?) is lost.  I do not really understand the meaning of tahara.  There is some hint that  is related to clarity, perhaps transparency.  In the book of Exodus, the description of a glimpse of heaven

 וְתַ֣חַת רַגְלָ֗יו כְּמַעֲשֵׂה֙ לִבְנַ֣ת הַסַּפִּ֔יר וּכְעֶ֥צֶם הַשָּׁמַ֖יִם לָטֹֽהַר׃

contains the tahor word.  It evokes  cleanliness.undisturbed uniformity, the absence of spots.

I would like to think that tahara, heavenliness, does not depend upon the crass judgments based upon appearance and smell.  I think of a disheveled, old person, with her distinctive aroma that emanates from foul emissions,  as a paradigm of purity - tahara.  I am reminded that the cleaning of the (rotting) dead is called tahara. 

I do not understand the world.  Here are the instructions.  The translation does not work