16 SCIENCE PROGRESS 



tion of; the respective enzymes. Anti-trypsin has also been 

 shown by Weinland to exist in the bodies of intestinal worms, 

 which are thus protected from the action of the pancreatic juice. 

 It is stated by this observer that the intestinal epithelium also 

 contains a similar substance; but recent work by Hamill has 

 failed to confirm this statement, although the mucous membrane 

 of the stomach was found to contain an anti-pepsin, as affirmed 

 by Weinland. These anti-bodies appear not to destroy the 

 enzyme, since a mixture of trypsin and anti-trypsin, at first 

 inactive, slowly recovers its proteoclastic power, apparently by 

 gradual disappearance of the anti-body. The mode of combina- 

 tion of toxin and anti-toxin has been shown by Craw to be of the 

 nature of adsorption, the characteristic of which process is that 

 it partakes of some of the properties of physical union and some 

 of those of chemical combination it is, in fact, as Ostwald puts 

 it, a combination in varying proportion. The dyeing of cotton 

 by Congo-red is such a process. If two pieces of cotton of the 

 same size are dyed in solutions of Congo-red, one of which is 

 twice the strength of the other, it is found that the cotton does 

 not take up equal quantities of dye from both, as it would if a 

 true chemical compound were formed, nor does it take up twice 

 the amount from the stronger solution, as it would if the process 

 were purely physical, such as solid solution ; it is found, in fact, 

 that relatively more is taken up from the more dilute solution ; 

 so that the amount taken up from that of twice the strength is 

 not double that taken up from the weaker, but less than this 

 indeed, x 2* , where x is greater than i and usually less than 2. 



It must suffice here to refer to the action of various electro- 

 lytes, especially that of OH" and H + ions, to which various 

 enzymes are differently sensitive. Pepsin is paralysed by OH~ 

 ions, while being increased in activity by H + ions. It appears 

 probable, from the researches of the present writer, that the 

 action of neutral salts may chiefly consist in facilitating or 

 otherwise the mutual adsorption of the enzyme and substrate. 



The enzymes connected with oxidation processes are 

 extremely sensitive to traces of certain metallic salts. Laccase 

 has been shown by Bertrand to be considerably increased in 

 activity by the presence of manganese. A similar relation of 

 tyrosinase to iron has been pointed out by Miss Durham. It is 

 not certain whether these enzymes are unable to exert this 

 activity in the absence of the metals referred to ; if this is the 



