What Are the Black Specks in My Cats Fur?

So over 1 year ago i got a cat from the humane society, her skin by her tail has always been kinda sensitive but now when i brush her by her tail there are these little black things in her fur. and she has white fur so i can see what they are really easily. well i put the black "things" under a microscope and its dried blood!!!!, but she has NO scape's at ALL!!!! i really don't know where they came from or anything. She doesn't have flees!!!!!! and she is losing her hair by her tail. Any advice or any help on what they are or what i can do?!?!?!?