The two features that make hair a good subject for establishing individual identity are scale structure and medullary index. The scale structure involves the length, color and diameter of the hair.
The medullary shape is the layer of hair shaft where the above attributes are featured. The medullar layer is an inside layer that runs down to the center of the cortex.
Giraffes have a compensatory precision in their movements, so that although it takes longer for them to respond to stimuli, they might do it more accuracy. The move fiber in a given nerve, the more fine-tunes a response to stimuli.
Answer:
it allows only some materials to pass through and leave the cell.
