PRENTISS: POLYDACTYLISM IN MAN AND DOMESTIC ANIMALS. 293 
Baumiiller (’92) figures the manus of a roebuck (Cervus caprea) 
which was composed of five digits. The abnormality was found on both 
fore feet. Baumiiller regards the extra digit as a pollex, and attributes 
its presence to reversion. 
Bateson (94) remarks with reference to polydactylism in the sheep 
and ox, that the extra digits are in all cases formed by duplication or 
variation. As to the development of digits 11 and v he asserts that 
“there is no such case.” 
In the ox, a number of cases of polydactylism have been observed 
and described. They may be divided into two groups: (1) manus or 
pes of three digits, all of nearly equal size, and borne on a single meta- 
carpal bone (Bateson, ’94, Figs. 114, 115, p. 375). In these cases the 
presence of both accessory hoofs (rudiments of 1 and v) in their 
normal positions makes it certain that the vestiges of digits m1 or v have 
not developed, but that either m1 or tv has become duplicated. Tour 
cases are described by Bateson, and it is stated by Goodman (’68) that 
the abnormality was common and frequently inherited in a herd of Eng- 
lish cattle. (2) Manus of four digits, 1 and v both being developed ; 
the accessory hoofs are located at the distal extremities of the extra 
digits ; each supernumerary digit is composed of a distinct metacarpal 
element, and digit 11 has in addition two small phalanges. Boas (90) 
describes two cases, and considers them good instances of reversionary 
polydactylism. 
B. OBSERVATIONS. 
Two cases of polydactylism in the manus of the ox have come under 
my observation. Both specimens had been disarticulated at the 
carpo-metacarpal joint, and the carpal bones were thus unfortunately 
lost ; they were right and left fore feet and probably belonged to one 
animal. Both are abnormally wide at the distal end of the cannon 
bone ; in each the hoof of the radial side is very broad and incompletely 
divided into two parts (Fig. W, p. 294, and Plate 21, Fig. 29). The 
accessory hoof of the ulnar side of the manus is normal in position, but 
that of the radial side is absent in both cases. 
In the left manus (Fig. 29) the skeletal parts are well formed. The 
metacarpus is of normal length, and is distinctly divided into three 
elements, each of which bears an articular head for a corresponding digit. 
These three elements represent three metacarpal bones, and we may 
designate them as Il, II, and 1v. m1 is larger than either of the 
others; its distal articular surface is unsymmetrical, as the trochlear ridge 
