CHAP. VIII.] 



MAMMAE. 



189 



*162. one side of the udder. The sketch given in Fig. 32, I. was taken 

 from a heifer having an arrangement intermediate between the 

 condition with four teats and that with six. As the figure shews, 

 on the left side there were three complete teats but on the right 

 side the third teat was incompletely separated from the second. 

 This third teat was joined to the second for its whole length but 

 had a separate pore. The animal which belonged to the St John's 

 College Dairy Farm was unfortunately sold before the first calf 

 was born, so 1 had no opportunity of seeing whether milk was 

 given by both these teats. The significance of such a case will 

 afterwards appear. 



In many mammals, such as the pig, rabbits, cats and dogs, 

 the mammae are distributed in two mammary lines along the 

 ventral surface. The number of the mamma? in such cases is noto- 

 riously variable, and in some respects this variation is interesting 

 and has a bearing on questions of the nature of Meristic Repetition. 

 If a number of such animals be examined it will be found that as 

 a rule there are the same number of glands on the two sides, and 

 that they are arranged in pairs, those of each pair standing at the 

 same level or nearly so. Nevertheless departures from this ar- 

 rangement are very frequent. Individuals are in the first place 

 commonlv found with a different number of mammae on the two 

 sides, and in such cases it is interesting to observe that together 

 w T ith the difference in the number of mammas on the two sides 



V 



V 



Fig. 33. Diagram of nipples in a male Bull-dog. On right side, four ; on left, 

 five ; the two anterior and two posterior being almost at the same levels. 

 umb. umbilicus. The dotted line shews the outline of the thorax. 



