BOOKS AND CURRENT LITERATURE 345 



Two sections of this fourth part are of especial interest to readers 

 of these columns: the paragraph on soil colloids and the discussion of 

 applications to biology. The former is very short (3 pages) and can- 

 not be commended. There are assumed without argument the con- 

 ception of humus as a definite colloidal substance and the idea of the 

 usual existence of colloidal (gel) silica in the soil, from both of which 

 assumptions the reviewer vigorously dissents. Under the applications 

 of colloid chemistry to biology Dr. Taylor discusses the equilibrium 

 between blood and oxygen; enzymes and the colloidal " inorganic fer- 

 ments" of Bredig; the phenomena of bacterial agglutination; and the 

 relations of toxins and antitoxins. To the biologist the treatment of 

 all of these subjects (except, perhaps, the oxygenation of the blood) 

 will seem sketchy and without proper perspective. Dr. Taylor's touch 

 is here far less sure than in his treatment of the subject matter of 

 colloid chemistry proper. One gathers that he has been interested 

 rather in finding biological illustrations of colloid principles than in 

 securing from colloid chemistry aid in the solution of biologic prob- 

 lems. One misses, also, any treatment of the swelling and shrinking 

 of organic gels — of imbibition and the water relations of living matter 

 and the associated non-living tissues. It would be too much to expect 

 the detailed discussion of these matters in a volume of the restricted 

 size and scope of Dr. Taylor's, but it is to be hoped that the examina- 

 tion and presentation of this important and disputed subject will be 

 undertaken soon by some biological colloid chemist or some "colloidal" 

 biologist. 



In the reviewer's opinion Dr. Taylor's book is to be recommended 

 to biologists not because of what it says of biology but because of what 

 it says of colloid chemistry. Nevertheless it is to be recommended 

 and that most insistently. If it accomplishes nothing else its perusal 

 may induce biologists to refrain from ascribing to convenient "colloidal" 

 actions all phenomena which they fail to understand. — E. E. Free. 



