The serpent is the animal, but the magical animal.
There is hardly anyone whose relation to a snake is neutral.
When you think of a snake, you are always in touch with racial instinct.
Horses and monkeys have snake phobia, as man has.
In primitive countries, you can easily see why man has acquired this instinct.
The Bedouins are afraid of scorpions and carry amulets to protect themselves, especially stones from certain Roman ruins.
So whenever a snake appears, you must think of a primordial feeling of fear.
The black color goes with this feeling, and also with the subterranean character of the snake. It is hidden and therefore dangerous.
As animal it symbolizes something unconscious; it is the instinctive movement or tendency; it shows the way to the hidden treasure, or it guards the treasure.
The dragon is the mythological form of the snake.
The snake has a fascinating appeal, a peculiar attraction through fear.
Some people are fascinated by this fear.
Things that are awe-inspiring and dangerous have an extraordinary attraction.
This combination of fear and attraction is shown, for instance, when a bird is hypnotized by a snake, for the bird flutters down to fight the snake, and then
becomes attracted and held by the snake.
The serpent shows the way to hidden things and expresses the introverting libido, which leads man to go beyond the point of safety, and beyond the limits of consciousness, as expressed by the deep crater.
The snake is also Yin, the dark female power.
The Chinese would not use the snake (i.e., dragon) as a symbol for Yin, but for Yang.
In Chinese [tradition], the Yin is symbolized by the tiger and the Yang by the dragon. ~Carl Jung, Seminar 1925, Page 102.