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Shark and Company 



This is the first and best of the early published figures of the strange spiral valve in 

 the large intestine of the shark. The shark is shown with abdomen slit open to show 

 the viscera. The valve is shown with half of the intestinal wall removed. Anatomist 

 Claude Perrault did an amazingly accurate job of portraying the valve, even though 

 in the seventeenth century its function had not been clearly understood. Even today, 

 this ancient drawing is valuable for illustrating simply the nature of the valve. 



Claude Perrault, 1671 



food were thrown to the sharks near a white plywood target which, 

 when pressed, caused a submerged bell to ring. 



On the third day of training, the food was tied to the center of the 

 target; in order for the sharks to get it, they had to press their snouts 

 against the target. When they got the food, the submerged bell rang. This 

 went on for 6 weeks, until the sharks were conditioned to associate the 

 target and the bell with food. 



At the beginning of the seventh week, an empty target was lowered 

 into the pen at feeding time. Now the shark had to bump the target, 

 ring the bell— and then find food elsewhere in the pen. It was given 10 

 seconds to get the food. If the shark didn't find the food, it went hungry. 



"The male quickly learned to press the target for reward food," Dr. 

 Clark reported, "and by the end of the week both the male and the 



