302 



Journal of Agricultural Research Voi. xvii, No. 6 



In Table VI are given coefficients of variation for a number of char- 

 acters for purposes of comparison with milk yield. The coefficients are 

 arranged in order of descending magnitude. 



Table VI. — Coefficients of variation for various characters 



Characters. 



Coefficient 

 of varia- 

 tion. 



Authority. 



Number of children per family (New South Wales) 



Area of comb (domestic fowl) 



Weight of spleen (English males) 



Size of litter (mouse) 



Lambs per birth (sheep) 



Dermal sensitivity (English males) 



Annual egg production (domestic fowl) 



Size of litter (Poland-China swine) 



Size of litter (Duroc-Jersey swine) 



Milk yield (total lactation) 



Milk yield (daily average) 



Fecundity o (horse) 



Heart weijiht (English males) 



Weight of kidneys (English males) 



Weight of liver (English males) 



Swiftness of flow (English males) 



Body weight (English males) 



Revised maximum daily milk yield (for given age) 



Weekly milk yield (Ayrshire cattle) 



Breathing capacity (English males) 



Strength of pull (English males) 



Weight of shell of egg (domestic fowl) 



Body weight (domestic fowl) 



Weight of albumen of egg (domestic fowl) 



Length of red blood corpuscles (Bufo tadpoles) 



Weight of yolk of egg (domestic fowl) 



Amount of fat in mixed milk (daily fluctuations) . . 

 Yield of mixed milk (daily fluctuations) 



Weight of egg (domestic fowl) 



Brain weight (Bavarian males) 



Length of forearm (English males) 



Length of femur ( French males) 



Length of egg (domestic fowl) 



Stature ( English males) 



Horizontal circumference of skull (English males) . . 

 Specific gravity of egg (domestic fowl) 



78 



Powys (25). 



Pearl and Pearl (14). 



Greenwood (4). 



Weldon (2q). 



Pearl (n). 



Pearson (19). 



Pearl and Surface (i;). 



Surface (27). 



Do. 

 Gavin (2). 



Do. 

 Calculated from data in Pearson(27). 

 Greenwood and Brown (5). 



Do. 



Do. 

 Pearson (lo)- 



Greenwood and Brown (5). 

 Gavin (j). 

 This paper. 

 Pearson (19). 



Do. 

 Curtis (r). 



Do. 



Do. 

 Pearson (22). 

 Curtis (j). 

 Pearl (70). 



Unpublished data in this labora- 

 tory. 

 Pearl and Surface (16). 

 Pearl (0). 



Pearson and Lee (,24). 

 Pearson (iq). 

 Pearl and Surface (.16). 

 Pearson and Lee (.24). 

 Macdonell (7). 

 Pearl and Surface (j6). 



a Fecundity here means the fraction which the actual number of offspring arising from a given number 

 of coverings is of the possible number of offspring under the circumstances. 



This table brings out the well-known fact, which has been discussed in 

 some detail by Pearl (9), Gavin (2), and others, that, in general, physio- 

 logical characters exhibit high coefficients of variation as compared with 

 strictly morphological characters. Characters which are intermediate in 

 their quantitative determination, as, for example, the length of the egg in 

 the domestic fowl, give coefficients of variation intermediate in value. 

 Purely physical characteristics which are usually regarded by physicists 

 and chemists as "constants," such as the specific gravity of eggs, show 

 very low coefficients of variation. 



It is of interest to compare the coefficients of variation for total yield 

 and absolute amount of fat in the mixed milk of a large herd with 

 those for milk yield as discussed in the present paper. It is seen that 

 the former are about 9, whereas the coefficients for milk yield give values 

 of about 17 to 25, depending upon whether cows of all ages or of a single 

 age are considered. 



In secular variation in the amount or quality of the mixed milk of a 

 large herd, individuality of the animal as a source of variation is entirely 



