Just a quick question.

Please clarify you question.

This is how I understand it:

You want to know how to change from human to a creature which is half animal and half human.

Questions about this:
Why do you want to know that?
Do you want to become half human, half animal? Like a mermaid?
Do you know any creature that exists that is half animal and half human?

No problem. You are already 100% human and 100% animal. So being half of each is already accomplished.

Human beings are mammals (e.g. horses, elephants, whales, mice, lions, bears, monkeys, and apes--all those furry things with teeth and milk glands).

Mammals are a class of animals. Other classes of animals are the birds (Aves), amphibians (frogs and salamanders), and fish. All of these creatures are animals and we are just one species among more than a million species of animals.

I have witnessed many such transformations. It can be induced by various liquids, but vodka shooters seems to be a popular choice.

asking is mostly correct. Since humans are animals, we can never be anything other than completely human and completely animal. We cannot be one half of either, since it is philosophically impossible for us to be 200% of anything.