MERISTIC VARIATION 47 



up to well-formed organs fully functional. Curiously enough super- 

 numerary mammae are more common in men than in women. 



Bateson l quotes Bruce as having found in 2 3 1 1 females fourteen 

 cases (0.605 percent), and in 1645 males forty-seven cases (2.857 

 per cent). In another series 315 subjects were examined, show- 

 ing twenty-four cases (7.6 per cent), nineteen being male and 

 five female. Bardeleben is also quoted as having examined 2736 

 recruits (all males, of course). In this series "637 cases (23.3 

 per cent) were seen, 2 1 9 being on the right side, 248 on the left, 

 and 170 on both sides." 



The largest number of supernumerary mammae ever recorded 

 was in a subject described by Neugebauer. 2 This patient had 

 five pairs of nipples, of which the fourth, numbered from above, 

 was the normal. When the child was being suckled milk oozed 

 from each of the uppermost pair, but all other supernumeraries 

 yielded milk only with pressure. 



Extra teats in cows are too common to need mention except to 

 call attention to their excessive number. The cow Rose, famous 

 for her record at the Illinois Station, 3 had in all eight mammae, 

 six of which were fairly well developed, though only four were 

 functional. 4 It is noticeable that supernumeraries are nearly 

 always posterior to the normal or else constitute a doubling of one 

 of the normals. Every milker knows by sad experience that these 

 supernumeraries are not only common but frequently functional. 



A close study of this subject shows that repetition of these 

 parts may be by pairs or singly ; that the repeated parts may be 

 on the same or on different levels ; that they may be out of line, 

 being in some cases very near the median, and that the normal 

 nipple may be doubled. From the latter fact we further establish 

 the point that meristic variation may occur in two ways, either 

 by addition to the series or by division of a normal number. We 

 shall find the same in teeth. 



1 Bateson, Materials, etc., pp. 182-183. 



2 Ibid. p. 183. 



3 See Bulletin No. 66. 



4 These supernumeraries were not symmetrically placed. On the right side the 

 two extra teats were placed behind the two functional, as is commonly the case ; 

 but on the left side only one supernumerary was so placed, while the other was 

 between the two functional teats. 



