188 



MERISTIC VARIATION. 



[part I. 



mammary Variation in other mammals. In connexion with the 

 case of Man it may be mentioned that supernumerary mamma 

 below and internal to the normal ones has been seen in Macacus 

 and in Cercopithecus patas, Sutton. J. B., Intern. Jour, of Med. 

 Sci., 1889, XCVII. pp. 2o2 and 253; in the Orang-utan, Owen, 

 Con/p. A nut., iii. p. 780. In many mammals the number of the 

 mammae is very inconstant even within the limits of species and 

 from the facts seen in such cases deductions may be drawn which 

 arc at once instructive as to the nature of mammarv Variation 

 and have an application to the morphology of Meristic Series in 

 general, of these I shall give examples taken from three species. 



'161. The first is that of the cow's udder. Normally the cow has 

 four teats of about equal size. Not unfrequently there are six 

 teats, of which four are large and may be said in the usual parlance 

 t<» be the " normal " ones, and two are small and placed posteriorly 

 to the others. A case of this kind is shewn in Fig. 32, II. Commonly 

 these extra teats give no milk, but in many cases they have been 

 known to do so. Their size and position vary greatly; sometimes 

 they are placed near the other teats as shewn in the figure, but I 

 have seen them very high up, almost in the fold between the 

 udder and the thighs. 



Very frequently, however, there is only one extra teat making 

 five in all, such an extra teat being so far as I know, always on 



Fig. 32. Supernumerary teats in two heifers. I. The third teat is completely 

 separate on the left side, but on the right side is united with the second. (The 

 cleft between the two is incorrectly represented as a sharp line ; there was no such 

 sharp line of demarcation; the skin being very slightly depressed in this place.) 

 II. Teats of the third pair both completely separate. 



