Science, boys and girls, is a mysterious and wonderful thing. Science allows us to look at how things work, like, for example, dog saliva. Dog saliva is a peculiar substance. It has quite different effects when applied to certain surfaces, say, glass, or, more particularly, a 6 oz. jelly glass with a picture of Rocky and Bullwinkle on it. Imagine that this glass might somehow have found it's way off the counter because it was left there with a thin coating of milk inside it, and then imagine that it was taken to the living room and licked inside and out - coated liberally with dog saliva - and then imagine that this glass was used in a couple spirited games of chase the rolling thing around the living room and yet it was not picked up, as the human owner of this glass was too overcome with ennui to deal with it right now. When the glass is finally picked up, it will prove to be covered with an invisible yet quite tangible - oh very tangible, boys and girls, yes, it can be felt and how - layer of slime. That doesn't even want to soak away. In fact it will take about 4 dedicated soapy washings to remove the slime.
Now, let us imagine that a bread knife and a cheese grater might also have found their way off the counter. Imagine further that the dogs are able, somehow, to apply their saliva to these objects without cutting their tongues into ribbons, although the human might evilly wish that just for once the bastards would get theirs, but not really, because that would be wrong, not to mention expensive if they had to go to the vet to get their god damn tongues sewed up. Let us imagine further, a household so terrible that a cheese grater could be taken under the bed and left there for an unspecified period of time. The cheese grater is made of metal covered with some vaguely suspect substance, possibly enamel, possibly lead paint. This is not the preferred household cheese grater but cheese grater #2, the back up grater that came from the Goodwill on a whim because who knows when you might need another cheese grater and anyway we can use it for camping. The bread knife, which was a nice knife until the wooden handle got all chewed up, jesus christ, what is wrong with these goddamn dogs, is stainless steel. The cheese grater was slightly coated with slime but not to the extent of the glass, and the knife was quite clean, both handle and blade.
So the scientist must therefore conclude that dog saliva has differing effects on differing materials and stainless steel is probably the best material for dog toys. All this points us of course to the notion of intelligent design, because clearly this kind of thing could not have come about just by chance. No, there must be a Designer, and that designer obviously has a dog's head, or such careful attention would not have been paid to dog saliva, and probably carries a set of scales around with him to weigh the souls of the dead. Anubis, all hail. Your existence has just been proven.
Side note: Hound dog saliva when coming out of the side of the mouth of a hound dog in the back yard has considerable tensile strength; to wit, leaves and small insects can get caught up with it and carried about, dangling, for a long time. Long enough to slam the door closed and say go wipe your nasty mouth you disgusting beast anyway.