chap, xiil] DIGITS : PIG. 383 



extra digits form another Minor Symmetry of their own. It is perhaps 

 worth noting that the metacarpal of the digit lettered d a in the form of 

 its head is nearly the optical image of that of III (d*), but this resem- 

 blance may be misleading and must not be insisted on. Coll. Surg. 

 Mus., Ter. Ser., 298. 

 572 Wild Boar. Two cases, apparently resembling the foregoing are 



described, from external examination only, in the wild boar by Geoffroy 

 St Hilaire, Hist, des Anom., 1. p. 696. 



Syndactylism in Artiodactyla. 



This phenomenon is known in the Ox and is common in the 

 Pig. In all cases the variation consists in a more or less complete 

 union or absence of division between the digits III and IV. Among 

 the many records of digital variation in the Pig no case relates to 

 union between a lateral and a chief digit, but it is always the two 

 chief digits III and IV that are united. (Compare the case of 

 Man, p. 358.) In this case there is therefore an absence of a 

 division in the middle plane of a bilateral Minor Symmetry, and 

 the parts that remain united are related to each other as optical 

 images. The phenomenon is thus the exact converse of the 

 variation consisting in a division along a plane of bilateral sym- 

 metry which was seen in the Horses Nos. 547 and 550. As was 

 remarked in speaking of similar variations in Man, it is to be 

 noticed that if the union is incomplete, as it commonly is, the 

 peripJteral parts are the least divided, the division becoming more 

 marked as the proximal parts are approached. 



In the normal Sheep according to Rosenberg 1 the metacarpals 

 II and V are distinct in the embryonic state, afterwards completely 

 uniting with III and IV. The same is presumably true of the Ox ; 

 but whether this be so or not, the digits II and V are in the 

 normal adult not represented by separate bones in the hind foot, 

 and in the fore foot V only is represented by the rudimentary 

 * bone articulating with the unciform. Unusual interest therefore 

 attaches to the observations made by Bo AS and by Kitt of the 

 development of lateral metacarpals and metatarsals (II and V) in 

 Calves having III and IV united. Note also that in two of Kitt's 

 cases there was not only a development of lateral digits but also 

 indications of a division occurring in them. Besides this, in the 

 right fore foot of one solid-hoofed Pig (No. 585) there is a slight 

 appearance of duplicity in the ungual phalanx of the lateral 

 digit V. 



On the other hand the reduction of accessory hoofs {ergots) in 

 Landois' case, No. 582, seems to be an example of a contrary 

 phenomenon ; for the connexion between the developed lateral 

 metacarpals and metatarsals in Kitt's case (No. 579) must be 

 taken as evidence that the accessory hoofs do really represent 

 II and V. 



1 Rosenberg, A., Z.f. w. Z., 1873, xxm. pp. 126 — 132, figs. 14, &c. 



