PART II, SERIES 1. OBSERVATIONS ON THE BODY 

 MEASUREMENTS AND ON THE WEIGHTS OP SOME 

 . ORGANS OP CAPTIVE GRAY NORWAY RATS 



HENRY H. DONALDSON 

 MATERIAL AND PROCEDURE 



The rats examined were all bred and reared by Doctor King. 

 For this study, series 1, 499 animals have been dissected ac- 

 cording to a uniform method by Miss Ruth Meeser. It was 

 planned to use about twenty rats of each sex in each genera- 

 tion, but, as the tables 1 and 2 show, this number has, on the 

 average, been slightly exceeded. 



In each case the body length and body weight were deter- 

 mined. The organs weighed were the brain and two of its 

 parts: the olfactory bulbs and the paraflocculi; also the 

 hypophysis, the thyroid, the suprarenals, and the gonads. To 

 interpret these data the values observed for each case were 

 referred to the corresponding values for either the wild gray 

 Norway or the albino rat taken from a series of tables found 

 in The Kat (Donaldson, '24), and the deviations from these 

 standards determined. In the text that follows, these tables 

 are distinguished by the numbers which they bear in the 

 publication just noted and the citations are in italics. Since 

 the effort is here being made to follow not only the way in 

 which the gray Norway rat in captivity departs from the 

 Albino, but also from the wild strain, in respect of the char- 

 acters studied, it would have been ideal could we have had 

 also a complete series of reference tables for the wild Norway 

 to be used for every comparison. Such reference data, how- 

 ever, are available only for the body length, body weight, and 

 the brain weight. For the other comparisons with the wild 

 strain, it has been necessary to use a series of short tables 



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