60 



Messrs. Dreyer, Ray, and Walker. [Sept. 30,. 



than threefold). The average tracheal constant (k) is 12 - 5 with an n of 

 - 70, which is the best n for these observations, and the average tracheal 

 percentage is - 873. It is seen that, as was the case in the guinea-pigs* 

 the variations of the tracheal constant show no periodicity, but the tracheal 

 percentage falls markedly, though not quite regularly (from T084 to 0'684). 

 If the tracheal area (T) is calculated by our formula, the average deviation 

 between the calculated and the observed figures is 6 - 43 per cent., while- 

 it is 13 - 39 per cent, (more than twice as great) when the area is calculated 

 in per cent, of body weight. If the value 071 be taken for n, the value of h 

 becomes 13 '4. 



Table IV.— Eabbit (grouped). 



Group. 



Numbers of individuals 

 from Table III in 

 group. 



Average body weight. 



Average radius of 

 trachea. 



Average area of tracheal 

 cross-section. 



O 



II 



Tracheal cross-section 

 as percentage of body- 

 weight. 



Cross-section calculated. 

 T = W°- 70 /*. 

 (Jc = 12 -5.) 



Difference between 

 cross-section calcu- 

 lated and observed. 



Cross-section calculal ed 

 as percentage (0 - 880) 

 of body-weight. 



Difference between 

 cross-section calcu- 

 lated and observed. 







grm. 



mm. 



sq. mm. 









per cent. 





per cent. 



A 



1—2 



955 



1 78 



9 95 



12 3 



1 -04 



9 75 



2 05 



8-4 



18 -45 



B 



3—4 



1215 



1 92 



11 -58 



12 5 



953 



11 -54 



35 



10 69 



8 33 



C 



5—7 



1633 



2 -14 



14 '47 



12 3 



0-886 



14 -2 



1 -9 



14 37 



7 



D 



8—11 



2145 



2 34 



17 '2 



12-5 



802 



17 -18 



0-12 



18 -88 



8-9 



E 



12—13 



2860 



2-56 



20 6 



12 -8 



0-72 



21 -02 



2 



25 -17 



18 16 









Averaj 



?e 



12 -5 



0-88 





1 28 





10 -91 



In Table IV the rabbits are arranged in the usual way in five groups. As- 

 i'n the case of the individual observations the best n is - 70, giving an average- 

 k of 12"5. The variations in the tracheal constants (for the groups) are small. 

 and are non-periodic, while the tracheal percentage falls with absolute- 

 regularity from 1-04 in the lightest group to 072 in the heaviest group. 

 Using the values just stated for % and k, the average percentage deviation 

 of the observed from the calculated figures is 1*28, while it is 10 - 91 (more- 

 than eight and a-half times as large) if the area be calculated as a percentage- 

 of the body weight. If % is taken as - 71, k becomes 13"4. 



Table V gives the figures for the tracheas of 10 ptarmigan purchased from, 

 a game-dealer. They had been shot for the market, and exhibit the greatest 

 range of weight that we were able to obtain, namely, from 460 grm. tc- 

 710 grm. The average tracheal constant (k) is 7'45 with an n (best n) of 

 0"7l, and the average tracheal percentage is 246. The variations of the 



