PRENTISS: POLYDACTYLISM IN MAN AND DOMESTIC ANIMALS. 261 
“Tn such a hallux there is increase in the number of phalangeal joints. 
This of course corresponds to the three-jointed pollex in man... . In the 
highest form of the reduplication the short toe is itself represented by two 
digits, making six in all. Of this, also, there are many grades. 
“Lastly, any of these conditions may be seen on one foot only, while the 
other foot shows one of the other states or is normally four-toed. Generally 
speaking, however, there is a fairly close symmetrical agreement between the 
two feet.” 
Thus we see that a single cross between the Dorking and Leghorn 
varieties produces all of the polydactylous abnormalities which investi- 
gators have so far observed in the fowl. 
The conditions presented are interesting and noteworthy from their 
structural similarity to the digital variations found in man and the 
Carnivora. For here, too, we find that the abnormalities are mainly 
confined to a reduced or modified digit, which becomes partially or 
completely doubled. 
Howes (’92) and Anthony (’99) regard these abnormalities as due to 
the splitting of the hallux, not as reversions to a five or six-toed ances- 
tor. Bateson and Saunders (:02, p. 137) evidently agree with them, for 
besides their allusions to “the reduplication” of the hallux, they class 
the abnormalities as “new characters” — “a palpable sport” (p. 137). 
The significance of their experiments and the bearing of “ Mendel’s 
law” upon polydactylism will be discussed later with other theoretical 
considerations. 
V. Polydactylism in Swine. 
A. LITERATURE. 
Although polydactylism is quite common in the pig, and many cases 
have been recorded, few careful descriptions have been given, and those 
deal only with the skeletal parts. As a consequence, very conflicting 
statements are made by different authors concerning the causes produc- 
tive of the conditions, some maintaining that polydactylism in the pig is 
atavistic, others that it is due to duplication of the whole foot, and still 
others that it is to be accounted for only by haphazard variation. 
Geoffroy St. Hilaire (32-37), Gurlt (77), Gegenbaur (’80), Bateson 
(94), and Werner (’97) have observed instances of digital variation in 
swine. Otto (’41), Ercolani (81), and Blane (’93) have given good 
descriptions of the skeletal parts of a few cases. 
Ercolani obtained data as to the skeletal structure in twenty-five 
