268 THE INTERNAL ENVIRONMENT OF THE BODY Part III 



Sugar Diabetes and Insulin Treatment. When the cells in the isles of 

 Langerhans fail to produce insulin, the body cannot use its sugar, no matter 

 how plentiful it is or how well digested. The oxidation of glucose stops, espe- 

 cially in the muscles, and glycogen is no longer stored in the liver and 

 muscles. Sugar accumulates in the blood, is excreted in the urine, and thus 

 is continually thrown away. In the meantime the starving body uses first its 

 fats and then its proteins in the progress of the disease of diabetes mellitus 

 that resulted fatally up to the time when insulin became known. The insulin 

 treatment of diabetes was first used in January 1922. Since then thousands 

 of persons have been able to live successfully by means of it. The saving of 

 all of them has been due to knowledge gained by experiments upon ani- 

 mals. 



In 1889 two European physicians, Oscar Minkowski and Joseph von 

 Mering, removed the pancreas from dogs in making studies of digestion. 

 Their caretaker noticed that there were unusual gatherings of flies about the 

 urine of these dogs and when the investigators examined it chemically, they 

 found that it contained quantities of sugar. They immediately tried to remedy 

 the diabetes by feeding the dogs extract of pancreas. But they were without 

 success because they were including the enzyme trypsinogen in the pan- 

 creatic juice, which becoming trypsin in the intestine destroyed the insulin, a 

 protein. In 1893, Minkowski published an account of the whole matter. Many 

 experiments followed, mostly unsuccessful because of the destruction of the 

 insulin. Later experiments brought more facts and more clues. Finally, 

 Banting, Best, Macleod, and Collip, investigators at the University of Toronto, 

 discovered a successful treatment and began it in 1922. Banting tied off the 

 pancreatic duct temporarily and, although this brought on bad symptoms, 

 those of diabetes were not among them. Collip destroyed the trypsin with 

 alcohol and acid and thus secured an effective extract of pancreas that in- 

 cluded insulin. This is essentially the same remedy which has been used ever 

 since. No cure for diabetes has been discovered and the extract can be taken 

 only by injection. 



Gastrointestinal Hormones 



These hormones work in series, each one preparing for the chemical action 

 of another secretion (Fig. 15.12). 



Gastrin. The arrival of food in the stomach stimulates the secretion of 

 gastrin by the cells in its lining. Gastrin in turn acts as a stimulant to the 

 production of the gastric juice. 



Secretin. When stimulated by the arrival of an acid food-mass from the 

 stomach, cells in the intestinal lining secrete the hormone secretin into the 

 blood. This in turn stimulates the pancreas to produce pancreatic juice and 

 the liver to secrete bile. 



