PREPARATION FOR THE STUDY OF BIOCHEMISTRY 27 



understanding of life which is to come therefore, we must learn to 

 rely with confidence upon relatively small and fluctuating disparities 

 between groups composed of very variable material. This can be 

 done in one way and in one way only, namely, by employing the methods 

 of the statistician whereby we may accurately gauge the relative 

 values of observations obtained with variable material, compute the 

 number of observations necessary to attain a given degree of certainty 

 or accuracy, place in their proper perspective extreme or overlapping 

 variations in aberrant individuals and, in short, render measurements 

 upon even such variable material as living organisms just as precise 

 as the measurements employed in quantitative analysis. 



The student of biochemistry would be well-advised therefore to 

 acquire the simple mathematical technique which is requisite for the 

 employment of statistical methods, 1 but he should remember that this 

 branch of mathematics above all others abounds in pitfalls for the 

 unwary and he should be sure that he perfectly comprehends the 

 simple fundamental principles which underlie these methods before he 

 attempts to put them into practice. 2 If the reader should desire to 

 gain a conception of the variety and scope of the possible applications 

 of the statistical method to problems of biochemistry, experimental 

 biology and agriculture, he may consult the recent work of Loeb and 

 Wasteneys upon the applicability of the Bunsen-Roscoe law to animal 

 heliotropism, 3 of Waynick upon the distribution of nitrifying bacteria 

 in soils 4 and of the author upon the growth of children. 5 



The Subdivisions of the Subject. In this work we will endeavor 

 to follow up the foodstuffs from the moment when they are partaken 

 of, to the moment when, after having circulated through the body and 

 partaken of its life, their final products are excreted. The subject- 

 matter is divided into six parts corresponding with various phases of 

 the cycle of changes which the foodstuffs undergo. The subdivisions 

 are as follows: 



Part I. The Foods, their properties, digestion, assimilation and 

 conversion into living matter or into reserve-materials. The considera- 

 tion of this phase of our subject takes us up to the point at which the 

 foodstuffs, subjected to certain modifications, have really been converted 

 into living protoplasm. This leads us naturally to the consideration 

 of the second phase of our subject, namely : 



1 The Student may consult G. Udney Yule: An Introduction to the Theory of 

 Statistics, London, 1911. For tables and formulae the student may refer to C. B. 

 Davenport: Statistical Methods, New York, 1904. 



2 Probably the best introduction to the fundamental conceptions of probability 

 which form the basis of the statistical method is contained in the classical little memoir 

 of W. A. Whitworth entitled Choice and Chance, Cambridge, 1901. 



3 Jour. Exper. Zool., 1917, 22, 187. 



4 D. D. Waynick: University of California Publications in Agricultural Sciences, 

 1918, 3, 243. 



* T. Brailsford Robertson: Am. Jour. Physiol., 1915, 37, 1 and 74; 1916, 41, 535, 

 and 547. 



