I shall now make a few observations on muscular irritability, as exemplified by the shark. That which is termed muscular irritability, and which is met with to a great degree in all cold-blooded animals, is well exemplified in the shark, which perhaps possesses it to a greater degree than other kinds of fish. I have seen a shark transfixed with a harpoon after it had been hooked, so as to cause the viscera to protrude; it was hoisted on deck, when, after a quarter of an hour had elapsed, the lower part was separated from the upper; (which detached lower portion for a long time displayed great powers of vitality;) the head and upper portion were afterwards thrown into the water, when the pectoral fins were moved as in the action of swimming. How long this irritability continued I cannot say, (but from other instances that I had seen, I should consider for a long period,) as it soon went astern of the ship. I have frequently seen the animal hauled on deck, the whole of the viscera extracted, and the body otherwise mangled when thrown overboard, swim for some distance in this mutilated state. Again, a shark has been hung up with the abdomen ripped open, the whole of the viscera extracted, and the head detached; yet symptoms of vitality, or rather muscular irritability, remained for three hours from the time of its removal from the water; and this frequently occasions the spectators to consider that the animal is in a state of suffering. It is only in the cold-blooded animals that we meet with it to such an extent; in the warm-blooded animals it occurs, but in a very slight degree.