PROBLEM 6. Hormones Help Regulate Cell Activities 



Fig. 242 This girl has dia- 

 betes. She has learned to in- 

 ject the amount of instdin 

 prescribed by her physician. 

 (encyclopaedia britannica 

 films, inc.) 



the disease is caused by a laci< of insulin 

 and that the insuHn has no connection 

 with the kidneys. The various steps in 

 the history of this discovery make an in- 

 teresting story. 



The first step was taken some time 

 before 1850 bv the great French physi- 

 ologist Claude Bernard, a pioneer in 

 experimental biology. Not satisfied with 

 speculation and obsei-vation, he per- 

 formed carefully controlled experiments 

 on animals. By means of some of these 

 experiments he showed that the liver 

 takes part in sugar metabolism. Because 

 of this Bernard suspected that it might 

 be the liver, rather than the kidneys, 

 that was not acting normally in diabetes. 

 But experiments to test the truth of this 

 theory showed it to be false. 



Then about 1890 an important dis- 

 covery was made. Two German in- 

 vestigators were interested in digestion, 

 particularly pancreatic digestion. They 

 had in their laboratory some dogs whose 

 pancreas had been removed. The labora- 

 tory helper who cared for the animals. 



a keen observer though knowing little 

 science, noticed that the urine of the 

 dogs that lacked a pancreas attracted 

 large numbers of flies. He reported 

 this seemingly unimportant observation. 

 The trained scientists, knowing that 

 flies are attracted to sweet liquids, sus- 

 pected that the excretions might contain 

 sugar. This proved to be true. There- 

 fore they reasoned that the presence of 

 sugar in the urine might have some con- 

 nection with the loss of the pancreas. 

 This was an entirely new idea. More 

 experiments were performed. It did not 

 take long to prove that a pancreas, and 

 not a kidney, condition caused an over- 

 supply of sugar in the blood and urine. 

 In the meantime, a biologist named 

 Langerhans had discovered little patches 

 of cells in the pancreas that were differ- 

 ent in structure from the rest of the 

 gland. It was suspected that these cells 

 might have something to do with con- 

 trolling the amount of sugar in the blood. 

 Autopsies (dissection after death) showed 

 that in diabetics many or all of these 



