The king of Egyptian gods, Amun, is often depicted with a ram's head. Anubis, god of the dead, has a jackal for a head. Horus, god of the sky, usually appears with a hawk's head. 

These are just some of the examples showing the weight put on animals in ancient Egypt. Animals had a special, godly prominence. 

This sacred status led them to be revered in life, but it could also lead to them being killed and mummified.

Any animal was fair game, from crocodiles to baboons and birds including falcons, hawks and ibis. Even rodents and snakes were among the millions of animals mummified as gifts for Egypt's gods. The animals were reared especially for that purpose. 

Some have since been excavated, but there are still thought to be millions lying dormant in Egypt's catacombs, untouched for more than 2,000 years.

Advances in technology means we can now peer inside these ancient animal mummies in unprecedented detail.

At Manchester Museum in the UK, researchers have carefully prepared about 60 animal mummies for display. While doing so, they X-ray- and CT-scanned hundreds of mummies.

The team discovered that some of the mummies do not necessarily contain the animal remains that they were expected to have. Some had partial skeletal remains and others had none at all. 

A few had the visible remains of their last meals inside their stomachs

One was even found to contain human bones. "There is a range of content in these mummies even though from the outside they look quite similar," says Lidija McKnight of the University of Manchester, who X-rayed the mummies now on display.

It is not clear why. It could be that there was so much demand for these mummies that there were not enough bones to go round.

Even a tiny bone, or an association with an animal, was believed to be enough to send a message to the gods.  

McKnight and colleagues also discovered that the animals were mummified quite differently to their human counterparts. "The analysis we've done with X-rays seems to suggest that the process they were using was quite basic," she says.

For example, it did not involve taking out their internal organs, as was done with humans.

The mummies were treated with a mixture of tree resin and beeswax, which would have acted as an antibacterial coating covering the animal. This was important to stop the mummies decomposing.

After this process they were simply wrapped up, McKnight explains.

A few even had the visible remains of their last meals inside their stomachs. "To preserve even the remains of the stomach contents means they must have desiccated and dried quite quickly. So no decomposition was able to take place before they were preserved." 

Humans wanted to be preserved so that they could travel to the next world. The goal for these animals was different. 

They were not expected to travel to the afterlife like humans. Instead they were sent as direct messengers to the gods. 

The idea was that the prayers of individuals could be answered by sending up these votive offerings, McKnight says. "They created an image of that animal that would be recognisable to the animal gods."

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