EXTRA TOES IN HORSE AND STEER 



B. O. Severson, State College, Pa. 



DR. MARK FRANCIS, of the 

 Texas Agricultural College and 

 College Experiment Station, has 

 kindly furnished the following 

 photographs of polydactylism in the 

 horse and steer. Fig. 13 is interesting 

 because it illustrates the same boi,ie 

 structure analogous to the case of 

 " Cloven Hoofed Percheron " in a recent 

 issue of the Journal. This is a type 

 of polydactylism which is the result 

 of the splitting of a single digit. 



Another type of polydactylism in the 

 horse is illustrated in Fig. 14, namely, 

 reversion to an ancestral form. In this 



case the extra digit at the pastern joint 

 is connected with the splint bone and is 

 in accordance of results shown by studies 

 on the evolution of the horse. The 

 horse having this variation was normal 

 in the other three legs. 



The skeletal bones of the two front 

 feet of a steer are shown in Fig. 12. The 

 bones of three well-developed digits are 

 present instead of two normal digits. 

 The photographs shows very distinctly 

 the continuation of the extra digit from 

 the splint bone. This again is a case of 

 polydactylism of the type known as 

 reversion to the ancestral form. 



SKELETAL BONES OF POLYDACTYLIC FEET OF STEER 



Where two normal digits should be present, three are found in this instance. The continua- 

 tion of the extra digit from the spHnt bone is clearly shown, and makes it apparent that this 

 is also a case of reversion to ancestral form. (Fig. 12.) 



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