chap, vii Enzymes and their Action 407 



the alimentary canal in mammals he investigated the sugar 

 relations of the beetroot, and not only found evidence of 

 its existence in the cells at the time of the renewal of 

 growth in the second year, but extracted it therefrom. It 

 was next observed by Berthelot in i860, in his researches 

 upon yeast and alcoholic fermentation, in the course of 

 which he showed that it is excreted from the cells of ttie 

 yeast plant, Berthelot named it ' ferment glucosique \ 

 In 1864 Bechamp proved its existence in several fungi 

 and in the petals of several flowers, especially those of 

 Robinia viscosa. It was named invertin in 1875 by 

 Donath. 



The distribution of invertase has been the subject of 

 much inquiry. It was found by Kosmann in buds in 1877 ; 

 in the rootlets of barley grains during germination by 

 Kjeldahl in 1878 ; in pollen-grains by Van Tieghem in 

 1886, and by the writer in 1893 ; in foliage leaves by Brown 

 and Morris in 1893 and by Gonnermann in 1899. 



Invertase was the first of the enzymes whose composition 

 was closely examined. An investigation into its con- 

 stitution was carried out by C. O'Sullivan and Tompson 

 in 1890. They concluded that it is of a very complex 

 character, composed of carbohydrate and protein substance 

 in particular proportions. 



The other enzymes of this group that have been dis- 

 covered are not so well known as invertase. The next in 

 importance is maltase or glucase, which hydrolyses malt 

 sugar to glucose. Its importance appears when we remem- 

 ber that maltose is the ultimate product of the action of 

 diastase on starch. Maltase was first discovered in 1886 

 by Cuisinier in malt and in certain other cereal grasses, 

 and was again observed in 1891 by Geduld in Maize. 

 Bourquelot detected it in Aspergillus in 1893, and in 

 Yeast two years later. 



Lactase, which splits milk sugar into glucose and 



