It is camel's stomach.

Camel is a ruminant.

Almost ruminants have four stomachs, but camel have three stomachs.

(The difference is little, so there is scalor who classfy camel into ruminant that have three stomachs).

When camel swallow a herbal fiber or water whole, , they will be most sent to the "first stomach". Bacteria, such as a lactic acid bacterium in the stomach and a protein decomposition bacillus, decompose a fiber.
The food most consumed and collected in "the first stomach" is once returned to a mouth, and a camel rebites it.

Next, they are sent to "the 2nd stomach" and "the 3rd stomach".

Gastric juice, such as "PEPUSHIN" and "Renin", is secreted with "the last stomach".

And it is decomposed completely, and protein serves as nutrition, and is absorbed by the whole body.

Since humnanbeing cannot do polite digestion and absorption like a camel, he needs to compensate with eating animal protein.