88 SHINKISHI HATAI 



relating to growth will not be discussed at length, but merely 

 mentioned as they come, in connection with the presentation 

 of the formulas and charts. 



The data used were secured mainly from two colonies of al- 

 bino rats: (1) a colony kept at The Wistar Institute (during 

 1911 and 1912), and (2) a colony kept at the University of Mis- 

 souri (during 1910 and 1911). For the latter, the present writer 

 is under great obligations to Professor Jackson, who not only 

 supplied numerous rats for the purpose of control examination, 

 but has also granted the free use of his entire collection of data 

 on the weight of the viscera. 



I take this opportunity therefore to acknowledge my indebted- 

 ness to Professor Jackson for his courtesy. 



In addition, I have secured some rats from both New Haven 

 and Chicago for the purpose of determining the range of vari- 

 ability under different climatic and nutritional conditions. For 

 these rats I am indebted to Professor Mendel of New Haven 

 and Professor Carr of Chicago, and I desire to thank both of 

 these gentlemen for their generous assistance. 



For the interpretation of the results which follow, it is of the 

 greatest importance to bear in mind that the animals examined 

 were nearly all less than one year old — a very few having at- 

 tained this age. If we take the nonnal span of life of the albino 

 rat as three years, then it is plain that we are dealing with rats 

 in the first third of their life and that the end of the records gives 

 the conditions at the close of the growing period only, leaving 

 untouched the changes which may be expected to occur during 

 the next two years. For the discussion of the span of life in 

 the albino rat, the reader is referred to Donaldson ('08, p. 

 368), and to Slonaker ('12). 



TECHNIQUE 



Although most of the organs are clearly marked off from the 

 surrounding tissues, and thus may be readily removed in an 

 exact manner, nevertheless I shall describe my method of dis- 

 section in detail so that others may be fully informed concern- 

 ing it. 



