Correlation and Application of Statistics to Problems of Heredity 97 



anticipate 9 , 9°/ chestnut and 90'1 °/ o non-chestnut foals, a result almost 

 exactly that observed. 



If we judged by A (iii), A (iv), and G, we should conclude that black and 

 brown had no factor for chestnut. In that case chestnut and bay crossed 

 with black and brown would produce no chestnut foals. This is flatly con- 

 tradicted by C, D, E and F, which indicate that browns and blacks can 

 contain a factor for chestnut. The only explanation is, perhaps, a rather 

 forced one, namely that the matings in A (iii), A (iv) and G were few in 

 number and possibly made from a very few sires of brown and black colour 

 without factors for chestnut, while C, D, E and F, providing far more 

 numerous matings, contained blacks and browns with such factors. C, D, E 

 and F, indeed, tend to confirm this, for when the sire is black or brown 

 there are far fewer chestnuts produced than when the dam is black or 

 brown; in the latter case the larger number of dams used would give a 

 greater chance of their carrying factors for chestnut. 



Galton himself by averaging up the likenesses in coat- colour of foal to 

 dam and to sire concluded that as some 32"83 °/ o of foals followed the colour 

 of their dam and 3175 °/ that of their sire, there was no prepotency, but 

 such an averaging method misses the possibility of discovering a prepotency 

 due to the presence or absence of "factors." The equality of male and female 

 hereditary influence is borne out by the long series B, but hardly by the other 

 and shorter series such as C and D*. Galton was very fully aware of what 

 he terms the "rudeness" of the data. He had been troubled with much the 

 same problems in considering hair colour ; but he had then obtained an 

 analysis of the pigments in human hair from Professor Sorby and the latter 

 investigator had shown the existence of two distinct pigments, one red and 

 one black. Sorby painted two trees in these two pigments extracted from 

 human hair, pictures which used to hang in Galton's dressing room and are 

 now in the Galton Laboratory. More recent microscopic investigation seems to 

 show that the same two pigments occur in the hair of horses and dogs, but that 

 the red pigment is diffused in the hair, i.e. "the whole ground substance of 

 the fibrillae is impregnated with it." On the other hand the black or melanine 

 pigment occurs in the form of pigment granules"}". On examination of a 

 number of specimens of horse hair in samples from ribs and mane of chestnut 

 horses, ranging from the golden chestnut of the Trakehnen stud to the 

 black chestnut, the diffused red pigment was found in all, but the pigment 

 granules varied from scarcely any in the golden and light chestnuts to close 

 packing in the dark and black chestnuts. This corresponds very closely to 

 the range of granular pigmentation found in passing from light red to dark 

 auburn hair in man. Such results suggest that it is very desirable to study 

 microscopically the distribution of the two pigments in the hair of horses' 



* For example in 124 matings of chestnut dam by brown or black sire there were only 

 6 chestnut foals, but in 126 matings of chestnut sire with black or brown dam there were 

 46 chestnut foals. 



t Pearson, Nettleship and Usher: Monograph on Albinism, Part II, pp. 319-345, Cambridge 

 University Press. 



pgiii 13 



