190 LECTURE XL 



being confined to the decomposition of aromatic glucosides ; 

 Kossmann indeed states that the diastatic ferments which 

 he obtained acted also on glucosides, but it is probable that 

 his extract contained more than one kind of ferment. 



(3) Ferments which convert cane-sugar into glucose: a 

 ferment of this kind, termed invertin, has been extracted from 

 Yeast ; it is probable that a similar ferment is present in 

 succulent fruits, for they commonly contain a mixture of 

 cane-sugar and glucose. 



(4) Ferments which convert proteids into peptones ; 

 these, which are only active in the presence of free acid, 

 are termed peptic ferments ; such a ferment has been found 

 in the latex of Carica Papaya and in that of Ficus Carica 

 (Wurtz and Bouchut), and in the liquid excretion of car- 

 nivorous plants (von Gorup-Besanez and Will). 



Von Gorup-Besanez believed that he had succeeded in extracting a 

 peptic ferment from germinating seeds (Vetch, Hemp, Flax, and Barley). 

 Krauch has pointed out that this result is not trustworthy, inasmuch as 

 the glycerin-extract of Vetch-seeds, prepared according to von Gorup- 

 Besanez' method, contains peptone to begin with (see last lecture, p. 173). 



These are the only ferments which have been actually 

 extracted, but it is probable that others may also be present 

 in plants. Thus, from the researches of Miintz and of von 

 Rechenberg, it appears that the quantity of free fatty acids 

 in oily seeds increases very much during germination, doubt- 

 less in consequence of the decomposition of fats into glycerin 

 and the respective fatty acids. It is well known that in 

 animals this decomposition is effected by a ferment con- 

 tained in the pancreatic secretion, and it may be fairly in- 

 ferred that it is effected by this means in plants also. In 

 fact Schiitzenberger states that when an oily seed is rubbed- 

 up with water, an emulsion is obtained in which glycerin 

 and free fatty acids soon make their appearance. Again, 

 there is, in the pancreatic secretion of animals, a ferment 

 (trypsin) which decomposes proteids with the formation of 

 crystallisable nitrogenous organic substances such as leucin 

 and tyrosin. We have learned that these amides are of com- 

 mon occurrence in plants, and it is possible that they may be 



