16 



THE STRUCTUEE OF MAX 



Eesorption of those portions of the mammary line which lie 

 between the primitive teats soon begins to take place, and in such 

 a manner that the originally elongated and fusiform eminences 

 become rounded. At a later stage, as above stated, these flatten 

 out, and extend at the same time into the subjacent tissues. 

 In 'this way they form the well-known button -like epidermal 

 proliferations, which have generally been considered to mark the 



first stage in the develop- 

 ment of the mammary 

 glands, a stage which is 

 immediately followed by 

 the formation of the so- 

 called mammary pits. 



Later on we shall have 

 to refer to the conclusions, 

 with respect to Man, to 

 be drawn from Schultze's 

 observation, but we may 

 now turn to the ques- 

 tion of the disposition of 

 the mammary glands on 

 the body. 



Although the position 

 of these organs may vary 

 greatly, the ventral side of 



the body has the prefer- 

 FIG. 12. SHOWING THE ARRANGEMENT OF THE , 



TEATS IN A DOG, in two longitudinal rows con- ence Oil account of the 

 verging towards the pelvic region. greater facility with which 



the young can reach the teats. The position in the postero- 

 ventral region, i.e. in the region of the groin, may be considered 

 the most primitive. The udder of some Ungulates, as is well 

 known, is found in this position, and the same is also the case 

 in the Cetacea. In the great group of the Carnivora, and in 

 the Pigs, the teats are found on the thoracic and abdominal 

 regions (Fig. 12), arranged in two rows converging towards the 

 pelvic region. In other groups, again, they are confined to the 

 pectoral region (e.g. Elephants, Sirenia, many Lemuroidea, Chirop- 

 tera, Apes, and Man). 



The great range of variation in the position of the teats and 

 mammary glands deserves careful attention, since it enables us to 

 satisfactorily explain the existence of so-called supernumerary 

 mammary glands and teats, which often occur in human beings 



