The demonstration of a hormone in plant tissues to be known as “glucokinin”

The demonstration by the writer, in collaboration with MacLeod, Banting, and Best, that active preparations of the internal secretion of the pancreas conferred upon the depancreatized dog the power of glycogen formation led at once to the idea that wherever glycogen occurred in nature, a hormone similar to that produced by the islet cells of the pancreas would probably be found. Three obvious places to look for such a substance were 1 tissues of lower animals rich in glycogen such as the clam, 2 yeast, 3 fungi. The writer 2 was immediately successful in demonstrating the presence of such a hormone in clam tissue. Yeast was also investigated continuously for many months, and on January 26, 1923, after more than a score of failures, an extract of yeast was obtained which produced marked hypoglycemia in a normal rabbit (blood sugar 0.046 per cent). Since that date extracts of yeasts which have similar properties have been prepared by five different methods. The administration of such a potent yeast extract to a depancreatized dog also caused a marked fall in the percentage amount of blood sugar and a great decrease in the hourly excretion of sugar. As the yeast organism is a plant of the least differentiated type in the vegetabile kingdom, the idea occurred to the writer that, as all plants are sugar burners as well as producers, the preparation of the sugar molecule for combustion in the protoplasmic fire of the plant cell might he quite a secondary affair and be dependent, as Winter and Smith 3 have suggested, on the preliminary formation of 7 glucose, the combustion of sugar or the polymerization of the same being primarily dependent upon presence of the 7 form of glucose.