No. 6.— CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY 
OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 
COLLEGE, UNDER THE DIRECTION OF KE. L. MARK, No. 141. 
Polydactylism in Man and the Domestic Animals, with especial 
Reference to Digital Variations in Swine. 
By C. W. PRENTISS. 
TABLE OF CONTENTS. 
PAGE PAGE 
Introduction =. sw owe ,o BED connected with meta- 
I. Historical survey .. . . 246 Carpal PEt. te hoya, toe 
II. Polydactylismin man . . 251 a. One supernumerary 
Ae vinterature: 9 a) <p cep se 2ol GIGI oan thaw ba ayers 284 
B.. Observations... . . 202 b. Two ieeraamiecar 
III. Polydactylism in carnivora. 255 digitss ss 97. 285 
Ay futersture ; % 3. 3 s « “255 C. Significance of yaviations 
B. Observations . . . . 267 observed? ("5,25 055288 
IV. Polydactylism in the foil . 259} VI. Polydactylism in ruminants 292 
V. Polydactylism inswine . . 261 A, Literatures, (6 ea. ale. Cee 
An Literature ~ os. 3 ea, ek B. Observations. . . 203 
B. Observations . . . 263| VII. Polydactylism in reecannae 296 
1. Manus in which thé su- A. hateratire 27 90 or 5 e208 
pernumerary digits are B. Observations. . . . 298 
independent of the nor- VIII. Theories of polyelduteien 2209 
mal digits” («<li «2710 1. External influences . . . 299 
a. One supernumerary 2. Internal influences . . . 800 
GIBIGy sits ggter'sen Sy ap os 2O a. Reversion . . 2) te, O00 
b. Two supernumerary b. Germinal aridtion ~ OU 
Gigits! 5 s,s ate canine Da oummmany i ts, fe a eaedn 
2. Manus in which hie su- Bibliogtaphiye jvc) gee ewes OOS 
pernumerary parts may Explanation of plates . ... . 3814 
be more or less closely 
Introduction. 
Tue frequent occurrence of extra digits on the extremities of both 
man and the domestic animals has attracted the attention of many 
anatomists during the past century. Various theories have been ad- 
vanced to account for the appearance of these digital abnormalities, 
and the opinions expressed by different investigators have been 
remarkably contradictory. 
VOL. XL. — NO. 6 1 
