374 MERISTIC VARIATION. [PART I. 



cartilaginous head of this bone rested in a pit on the tendon of 

 the flexor brevis digitorum at the level of the end of first third of 

 the cannon-bone, and peripherally it bore an end-phalanx and 

 daw-like hunt', properly articulating. Xo splint-bones present. 

 [Other details given : it was suggested that the bent bone re- 

 presented an extra ' metacarpal ' and first and second phalanx.] 

 VON NATIM-SITS, H., Die Srlmf:uclit, 1S80, p. 143. 

 556. Capreolus caprea (Roebuck), 2 yr. old, killed in district 

 of Betzenstein, having a slender fifth digit on the inside of each 

 fore foot. In the left there was a small, conical metacarpal 

 element, bearing a digit with three phalanges. The right extra 

 digit had a longer metacarpal piece with epiphysis, but in it 

 there were only two phalanges. Each bore a hoof of about the 

 size of those of II or V. The hoofs curved outwards. BAU- 

 MULLER, C., Abh. naturh. Ges. Numb., ix. 1892, p. 53, PL 



Other cases of polydactyle Pecora mostly fall into two groups : 



(1) Examples of limbs having three digits borne by a large 

 cannon-bone made up of three metatarsal or metacarpal elements, 

 grouped in one system of Symmetry. The axis of Symmetry is 

 then deflected from the normal position, and instead of falling 

 between two digits it approaches more or less to the central line 

 of the middle of the three digits. The degree to which this change 

 of Symmetry takes place corresponds irregularly with the extent 

 to which the innermost digit is developed. This form is known in 

 the Ox only [? Goat]. 



(2) Limbs in which the series of digits has two more or less 

 definite axes of Minor Symmetry. Both of the systems of Svm- 



V V V *> 



metry thus funned are in addition arranged about one common 

 axis of Symmetry. The nature of this condition will be discussed 

 later. It occurs in Ox, Sheep, Roebuck and Deer. 



(1) Three digits in one system of Symmetry. 



55 1. Calf. Right manus (Fig. 114) having three digits borne by a 

 single cannon-bone. This is an old specimen of unknown history 

 which was kindly sent to me by Mr \T. L. Sclater for examination. 



Of the carpal bones only the distal row remains, containing a trap- 

 ezoido-magnum and unciform nut differing visibly from the normal. 

 The cannon-bone spreads at about its middle into three sub-equal parts, 

 each ending in a separate articular head bearing a trochlear ridge. 

 Between these articular surfaces the only point of difference was that 

 in that of the middle digit (b), the trochlear ridge was rather nearer to 

 the outer surface of the joint, not dividing it into two halves as usual 

 (see figure). The foramen for entrance of the nutrient vessel was in 

 the channel between the external and middle digits. This channel was 

 very slightly deeper than the corresponding channel between the 

 middle and inner digits. Each articular head bore a digit, well formed, 



