A kagune is composed of Rc cells, which flow just like blood, can become as solid as teeth and can be described as “liquid muscles”. A kagune can be repeatedly hardened and softened at will by the ghoul.
"You know why a Spider Lily is called the flower of separation? It’s because the leaves and the flowers can never meet. The flowers can only blossom when the leaves are all withered away. They miss one another to grow the sprout and bloom the flowers, but in the end they leave their yearning for each other and never unite. Isn’t it beautiful? Even in death, they seem to miss each other like lovers." — The Bride of the Water God