My father worked at a lab when I was as kid (1960 or so) and it closed, he brought home all kinds of cool stuff. One was a jar of pure mercury, about 1/3 of a cup. Us kids found it and played with all the time, I even put it in my mouth, it felt really strange. I subsequently graduated with honors from Johns Hopkins University.
I don't know if you were really ingesting the mercury by rollling it in your mouth. I had a vial of it too, as a kid, because my dad was a science teacher and brought it home. It was in the silvery form.
The problem with the mercury in the vaccines is that it is applied to babies whose immune systems and physical development is not at a level where they can withstand the effects. Just as when a baby is born, it does not look like a miniature adult, his/her internal development is not mature either. He is growing iside as well as outside, and high levels of mercury interferes with the proper development of important neuro-pathways, etc. There is a narrow window, as I understand it, when those pathways can be built and further development cannot take place until the neuropathways are in place. Some doctors point to the autistic's ubiquitous "sideways" glance (where the child never looks directly at you) as a symptom, for instance, that the rods and the cones in the eyes are not developed correctly.
The few autistics who have recovered tell of sort of a "tunnel vision" where the focus of their vision is off to the side. This is a problem that many adults have with autistics as they fuss at the child to "look at me" and the child is looking at them out of the corner of his eye -- which is the only spot he can see clearly.
My grandson had 4 times the acceptable levels of mercury in his system when he was tested, just from his baby shots.
I might add that if you were a kid in the 1960s, you also were not subjected to the same number of juvenile shots that the babies have now. There was no MMR vaccine, for instance, no hepatitus (which they get before leaving the hopital) no chickenpox, no rubella, etc.
The shots are all useful, but they really should be spaced, instead of given all at once as they often are now so that they don't overwhelm the immune system. We really think my grandson was damaged by the shots -- the change was so sudden. Sometimes its the child's individual immune system that is at fault, which is why not all children suffer ill effects. Just like some children have allergies and some don't, some children are sensitive to this mercury and some aren't.
Pure Mercury is odd that way. Because it has such a strong attraction to itself (note the bend of the meniscus) compared to other things, that large quantities of it tend to stay inert for a long time...however, if it is broken into smaller bits, by say dropping a vial of it, it forms these little tiny balls, which will evaporate and combine with other things. Thus very small quantities of mercury are often far more dangerous than large quantities. It's mostly about surface area relative to volume.
As for mercury which is chemically combined with other elements already, that is a whole different thing.