BODY LENGTH ON BODY WEIGHT 87 



The charts serve to show the form of the graph of growth in 

 each instance, but the precise weight values of the organs are to 

 be read from the tables. For those who desire to find the weight 

 of an organ in a rat of any body length or body weight a series of 

 values — computed by the aid of the appropriate formulas — are 

 given in tables 68-71 inclusive. 



In making these tables the determinations for the correspond- 

 ing body weights for each millimeter of length in each sex were 

 first made by formulas (2 a) and (2 b) and the body weights so ob- 

 tained were then used in computing the weights of the several 

 organs. 



In table 72 for the thymus however, it was found necessary to 

 enter the weight values of the organ according to the age of the 

 rat. 



In table 73 the computed weight of the thymus on body weight 

 is given on the assumption that the body weights are normal to 

 age in conformity with the data in table 62. 



2. Methods of examination and graphs. Unless otherwise 

 stated the following determinations were made on stock Albinos 

 taken from the colony at The Wistar Institute. The animals 

 were killed with chloroform twenty hours after the last feeding 

 and were dissected according to a fixed procedure. 



3. Body length on body weight. Technic: Immediately after 

 killing the rat was laid on its back and gently extended — the 

 tail being drawn out straight. With jointed calipers the dis- 

 tance from the tip of the nose to the tip of the tail was taken 

 and its values in millimeters found by applying the points to a 

 scale. Next the distance from the tip of the nose to the center 

 of the anus was found and its value in millimeters determined 

 in the same way. These measurements give first the total 

 length, second, the body length and by the difference, the tail 

 length. 



Chart 6 gives the body length on the body weight. The data 

 used are given in table 68. The values were computed by for- 

 mula (1). The graphs show that for a given body weight the 

 male has the greater body length. Donaldson '09; Donaldson 

 and Hatai '11. 



