348 SCIENCE PROGRESS. 



This method, in some cases, yields very striking results, 

 although the preliminary difficulties of dissection are 

 very great. One of the most successful instances of 

 its application is given by Marshall Ward (10) in his ex- 

 periments upon rkamnase, an enzyme causing decomposition 

 of a glucoside present in the fruit of Rkamnus infectorius, 

 the so-called " Persian berry". This fruit yields a valuable 

 dye of a bright yellow colour, which is one of the products 

 of the splitting up of the glucoside. On preparing a solu- 

 tion of the glucoside from the pericarp of the fruit, and 

 putting a small piece of the suspected tissue upon its 

 surface, so that it floated, the action was visible in the 

 course of a few minutes. In ten minutes the floating piece 

 of tissue was covered with a golden-yellow precipitate of 

 the colouring matter ; in twenty minutes clouds of the same 

 precipitate were sinking through the solution, and in less 

 than an hour the bottom of the test tube which contained 

 it was covered by a layer nearly two millimetres deep. 



Nor is it only with glucoside ferments that this method 

 has succeeded. Brown and Morris (4) detected diastase 

 in particular cells by isolating plates of them, and warming 

 them on the surface of gelatinised starch paste. Where the 

 particular cells rested, the starch became liquefied and sugar 

 was formed. Strasburger showed the presence of the same 

 body in pollen tubes, by allowing them to grow in solutions 

 containing starch, when again hydrolysis took place. 



In cases where the enzyme exists side by side in one 

 cell with the body in which it works, its presence may 

 be noted by warming the tissue containing them to about 

 40 C, for some time. Microscopic examination will then 

 be sufficient to show where the action is taking place ; it 

 the body be solid, as in the case of starch or aleurone, the 

 disappearance of the grains will at once be evident ; if it be 

 in solution, as in that of sugar or inuline, micro-chemical tests 

 can easily be applied. 



By these various means the locality of the ferment- 

 containing tissue can in most cases be satisfactorily estab- 

 lished, and a study of its distribution renders evident a 

 variable degree of differentiation, extending from the simple 



