DIGESTION 253 



the juice of the Fig-tree (Ficus carica), and the leaves of 

 certain species of Agave. How far these are identical, or 

 whether they present specific differences, appears at present 

 uncertain. They are all active in faintly acid solutions, 

 but the most favourable concentration appears to vary. 

 The enzyme of the Kachree gourd is most effective when 

 the medium is faintly alkaline, whereas that of the lupin 

 seed is inoperative under these conditions. Too much 

 stress must not, however, be laid upon this point, as the 

 enzymes have not been prepared in any case in anything 

 like a pure condition. 



Kecently Vines has found that members of the erepsin 

 class are very widespread in plants, occurring in almost all 

 parts of them. His researches suggest that possibly the 

 so-called trypsins are mixtures of pepsin and erepsin. 



The action of all these proteoclastic enzymes is pro- 

 bably one of hydrolysis, though it is difficult to prove it by 

 analysis. 



Eennet occurs in many seeds, in some cases in the 

 germinating, and in others in the resting, condition. It 

 has also a wide distribution in the vegetative and floral 

 parts of various plants. Whether it is really proteoclastic 

 in the vegetable organism it is hard to say, as the details 

 of its action are unknown. It is so in the animal body. 



The enzymes which decompose glucosides, as we have 

 already seen, are numerous and varied in their distribution, 

 occurring in various fungi and lichens as well as in the 

 higher plants. Their action may be illustrated by the 

 behaviour of emulsin, which exists in quantity in the seeds 

 of the bitter Almond and in the vegetative parts of the 

 Cherry-laurel (Prunus Laurocerasus). It splits up the 

 glucoside amygdalin according to the equation 



C 20 H 27 NO H + 2H 2 = C 7 H 4 + HCN + 2(C 6 H 12 6 ) 



Amygdalin Benzoic Prussia Glucose 



aldehyde acid 



This is, as in other cases, a process of hydrolysis. Myrosin, 

 another of the group, is peculiar in that it effects its 



