1912.] The Size of the Trachea in Warm-Blooded Animals. 65 



it appears that the value J for n gives a deviation T29 times as great as 

 that obtained with the best n, while if the value of n is taken as f- the 

 deviation is 1 - 51 times as great as that with the best n. 



Accordingly, it is clear that if an approximate value of n is employed for 

 the sake of convenience in rapid calculation it is, as a rule, preferable to 

 use the value \ rather than f. But wherever observations covering a wide 

 range of weight are concerned it is essential to make use of the " best n " 

 in order to obtain reliable results. In this connection it may be noted 

 incidentally as a point of interest that the ratio between the deviations just 

 quoted for n = ■§ and n = best n, namely, 3"81/2 - 52 (i.e. l'ol), proves to be 

 practically identical with the corresponding ratio already given elsewhere (2) 

 in the case of the blood volume, namely, 2-08/T39 (i.e. 1*5). 



Conclusion. 



Within a wide range of weight in any given species of warm-blooded 

 animal the sectional area of the lumen of the trachea is proportional to the 

 body surface, and can be calculated from the body weight by means of the 

 formula T = W n /k, where n has the value O'70-0 - 72 and k is the constant to 

 be ascertained for each particular species. 



REFERENCES. 



1. Dreyer, G., and Ray, W., 1910, " The Blood Volume of Mammals, as determined by 



Experiments upon Rabbits, Guinea-pigs, and Mice, and its Relationship to the 

 Body Weight and to the Surface Area, expressed in a Formula," ' Phil. Trans.,' 

 B, vol. 201, p. 133. 



2. Dreyer, G., and Ray, W., 1911, "Further Experiments upon the Blood Volume of 



Mammals and its Relation to the Surface Area of the Body," ' Phil. Trans.,' B, 

 vol. 202, p. 191. 



3. Dreyer, G., Ray, W., and Walker, E. W. Ainley, 1912, "The Size of the Aorta in 



certain Animals and its Relation to their Body Weight," 'Journ. Physiol., 

 vol. 44, p. xviii. 



4. Dreyer, G., Ray, W., and Walker, E. W. Ainley, 1912, "The Size of the Aorta in 



Warm-blooded Animals and its Relationship to the Body Weight and to the 

 Surface Area, expressed in a Formula," 'Roy. Soc. Proc.,' this vol., p. 39. 



5. Dreyer, G., Ray, W., and Walker, E. W. Ainley, 1912, "The Relation between the 



Sectional Area of the Trachea and the Body Weight in certain Animals," 

 ' Journ. Physiol.,' vol. 45, p. vii. 



6. Meeh, K., 1879, " Oberflachenmessungen des menschlichen Korpers," ' Zeitschr. f. 



Biologie,' vol. 15, p. 425. 



VOL. LXXXVI. — B. 



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