Makch 28, 1913] 



SCIENCE 



491 



significance the bearing of these investigations 

 on the life conditions which preceded the 

 Cambrian, is far-reaching, and must pave the 

 way to a repair of our conceptions of it and 

 gives us, too, a certain hope that unremitted 

 diligence may bring to our distinguished pro- 

 tagonist of Precambrian life a sure and firm 

 reward. 



John M. Clarke 



Nutritional Physiology. By Percy G. Stiles, 

 Assistant Professor of Physiology in Sim- 

 mons College; Instructor in Physiology and 

 Personal Hygiene in the Massachusetts In- 

 stitute of Technology, Boston. 12mo of 271 

 pages, illustrated. Philadelphia and Lon- 

 don, W. B. Saunders Company. 1912. 

 Cloth. $1.25 net. 



This little volume is a most welcome addi- 

 tion to the literature of nutrition. It is sel- 

 dom that as much information of a reliable 

 and useful kind is condensed in a publication 

 of this size. The author well states that " the 

 making of the book has been a study in elimi- 

 nation." He also states that it is intended to 

 be used with other books and suggests the de- 

 sirability of supplementary reading upon gen- 

 eral biology, human anatomy, food chemistry 

 and dietetics. We are informed that the key- 

 word of the discussion is energy. The author 

 has given us a careful and discriminating 

 study of the best existing scientific evidence 

 related to the physiological phases of human 

 nutrition and he has treated his subject in 

 language that is notably clear. His discus- 

 sion is well organized and he has exercised a 

 reasonable caution in his affirmations. Chem- 

 ical formulae and minute details have been ex- 

 cluded from the text and " used but sparingly 

 in the notes," for " a certain preliminary 

 knowledge of elementary science is assumed." 

 The volume deals with processes rather than 

 with chemical or physiological details. For in- 

 stance, in discussing the unlikeness of the 

 individual proteins on the basis of the " build- 

 ing stones " into which they may be sepa- 

 rated, no detailed list is given of the protein 

 cleavage products, but at the same time the 

 general bearing of the knowledge we now have 



in regard to protein cleavage and the nutritive 

 relation of single food proteins upon the de- 

 velopment of body proteins is clearly and 

 fully presented. The origin of urea is dis- 

 cussed, but it is assumed that the student is 

 familiar with the chemical reactions involved. 

 In fact, we have presented to us the philos- 

 ophy of nutrition minus minute chemical and 

 physiological details. The evident intention 

 is to give to the student a point of view and 

 this purpose is accomplished with eminent 

 success. 



One of the characteristic features of this 

 book is the type of illustrations used in order 

 to make clear certain metabolic processes and 

 nutritive relations. For instance, in dealing 

 with the difference in the constructive value 

 of the individual proteins, comparison is made 

 to a house that is pulled down in order that 

 another may be erected from its timbers. " If 

 the second house is of an architecture entirely 

 unlike that of the first, there will be many 

 unavailable pieces to discard and the new 

 building will be smaller than the old. It is 

 not at all unlikely that the misfit fragments 

 of building material will go into the cellar of 

 the new house, later to be used as fuel. This 

 is just what the body does." The structure of 

 a molecule of food protein is also compared to 

 type set up in a printed page. If this type is 

 allowed to fall apart, it is a symbol of diges- 

 tion and unless this is used to set up again 

 exactly the same matter, there will be unused 

 letters, just as in the human body protein 

 building stones will be used for fuel purposes 

 and not for construction unless the food pro- 

 teins and the body proteins are alike in con- 

 stitution. Familiar illustrations of this apt 

 character are frequently used throughout the 

 volume. 



If any one portion of this volume is to be 

 commended above another, it is the chapter 

 upon the hygiene of nutrition. Though cov- 

 ering but twenty-three pages, this chapter has 

 more value in its relation to practical dietetics 

 than some whole volumes written by a less 

 scholarly and discriminating author. In dis- 

 cussing nervous conditions as relating to di- 

 gestion, some space is given to the treatment 



