There are some things you'd rather not know.
I was trying to finally find out what the gelatin in film emulsion is made of. Here are some gross things I found at Howstuffworks
The gelatin you eat in Jell-O comes from the collagen in cow or pig bones, hooves, and connective tissues. To make gelatin, manufacturers grind up these various parts and pre-treat them with either a strong acid or a strong base to break down cellular structures and release proteins like collagen. After pre-treatment, the resulting mixture is boiled. During this process, the large collagen protein ends up being partially broken down, and the resulting product is called gelatin. The gelatin is easily extracted because it forms a layer on the surface of the boiling mixture.
Think about that when you eat Jell-O next time. Oh, and don't forget this:
Here is a list of some other foods that commonly contain gelatin:
* gummy bears
* sour cream
* cream cheese
* cake icing and frosting
* marshmallows
* soups, sauces and gravies
* canned ham and chicken
* corned beef
* sausage
Gelatin is even used to make the coating for pills that makes them easier to swallow. It's also in cosmetics, lozenges, and ointments.
Regarding photography:
It is likely that few people would be aware of a connection between the photographs carried in their wallets or handbags and such things as a bowl of jelly, a marshmallow confection, a pharmaceutical capsule or the hog and cattle industries.To date no suitable substitute for gelatin has been found in the manufacture of photographic film or paper.Gelatin for photographic use is generally made from ossein derived from bone.