Kidney always so simple; in cartilaginous fish and some amphibians, there is also a shorter duct, similar to the amniote ureter, which drains the posterior (metanephric) parts of the kidney, and joins with the archinephric duct at the bladder or cloaca. Indeed, in many cartilaginous fish, the anterior portion of the kidney may degenerate or cease to function altogether in the adult. In the most primitive vertebrates, the hagfish and lampreys, the kidney is unusually simple: it consists of a row of nephrons, each emptying directly into the archinephric duct. Invertebrates may possess excretory organs that are sometimes referred to as
Pig bladder Mob football, Medieval football, and La soule.) For centuries before the invention of the paint tube, artists used to store their paints in pig bladders. When the artist was ready to use the paint, they would puncture a hole in the bladder and squeeze out the desired amount of paint. They would have to mend the hole when finished and the whole process was quite messy. The oil paint tube was invented in 1841, as the primary packaging of paints for transport and storage. In the bian lian ("face changing") style of Chinese opera, painted pig bladders were used as