DIGESTION 267 



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. 



The action of all these proteolytic enzymes is probably 

 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 proteolytic 

 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 U -f 2H^O = C 7 H 4 + HCN + 2(C 6 H 12 6 ) 



Amygdalin Benzole Prussic 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 

 characteristic decomposition without causing the incorpora- 

 tion of water during the process, thus : 



C IO H, 8 NKS. 2 0, = C.H.CNS + C 6 H, ,0, + KHS0 4 



Sinigrin Sulpho-cyanate Glucose Potassium- 



of allyl hydrogen 



sulphate 



Others, such as rhamnase, existing in the seeds of Rhamnus 

 infectorius, eryihrozym in the Madder, gaultherase in the 



