436 



ORGAN SYSTEMS OF MAN 



few weeks. The salient point that came out 

 in the early experiments was the appear- 

 ance of large quantities of sugar ( glucose ) 

 in the urine of such operated dogs. The 

 two German workers who first performed 

 these operations noticed that ants were at- 

 tracted to the cages of these dogs and found 

 that it was the sugar in the urine which was 

 attracting them. This reminded them of 

 human diabetes, a disease that had been 

 known for centuries. A long series of experi- 

 ments followed by workers all over the 

 world, and it was soon proven conclusively 

 that the small groups of cells in the pan- 

 creas, called the Islets of Langerhans, pro- 

 duced a hormone called insulin that was 

 responsible for retaining and storing sugar 

 in the body. If these islets were destroyed, 

 as in the case of human diabetes, sugar no 

 longer was retained in the liver and other 

 tissues, but poured out through the kidneys 

 into the urine and was lost from the body. 

 This was a great discovery but what could 

 be done about it now that the cause of this 

 dread disease was known? 



The first step was to try to find a substi- 

 tute for the non-functioning islets. Feeding 

 the whole pancreas to depancreatized dogs 

 I ailed to produce the slightest effect. The 

 hormone was digested in the alimentary 

 tract; consequently, it never got into the 

 blood stream where it could be carried to 

 the liver and tissues in which it would work. 

 The next step was to inject an extract into 

 the body, but because of the difficulty en- 

 countered in getting a pure product, no 

 satisfactory results were obtained for 20 

 years. During this long period experi- 

 menters were attempting to obtain a pure 

 hormone from the whole glands of various 

 animals, mostly domestic animals such as 

 cattle, sheep, and hogs. 



It occurred to a young Canadian physi- 

 cian. Dr. Frederick Banting, that perhaps 

 the digestive enzymes produced by the 

 pancreas destroyed the insulin before it 

 could be extracted. This was later shown to 

 be true. Banting reasoned that since the 



embryonic pancreas was known to produce 

 the islet tissue before the enzymes ap- 

 peared in the pancreas, if such glands were 

 used, perhaps the hormone could be iso- 

 lated in an active state. In 1922, he and three 

 other men — Best, McLoed, and Collip — 

 working together, set out to isolate the hor- 

 mone. After a great deal of labor, they 

 eventually prepared a product which 

 caused no ill effects on the dogs when in- 

 jected under their skin and which cured 

 their diabetes. It was a short step to the 

 treatment of humans, where success was 

 immediate. The thousands of diabetics then 

 had, for the first time, some means of stav- 

 ing off an early death from a disease that 

 had always been fatal. 



Insulin was produced in more concen- 

 trated and more purified form during the 

 ensuing years until today the product is 

 responsible for the near-normal lives of 

 hundreds of thousands of men, women, and 

 children. Someday it may be possible t(> 

 take the hormone by mouth, but at present 

 it still must be injected under the skin at 

 rather frequent intervals depending on the 

 severity of the disease. 



The nature of diabetes. Without treat- 

 ment a diabetic suffers from insatiable 

 thirst, excessive urination, a gradual loss 

 in weight, general body weakness, and 

 finally a coma which terminates in death. 

 During this course the sugar in the blood 

 and urine is found, by measurement, to be 

 abnormally high (as much as 8 per cent in 

 the urine), the liver loses its glycogen and 

 finally, in the coma state, acetone and par- 

 tially degraded fats also appear in the 

 blood and urine. Before death the acetone 

 may reach such concentrations that it can 

 be detected on the breath. All of these 

 symptoms are immediately relieved with 

 the administration of insulin. 



The first, most obvious function of insulin 

 is to maintain normal carbohydrate metabo- 

 lism in the body. For some reason, in the 

 absence of insulin the liver fails to store 

 glycogen and glucose is oxidized very 



