16 THE STRUCTURE OF MAN 
Resorption 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-lke 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 
a the body has the prefer- 
Fic. 12.—SHOWING THE ARRANGEMENT OF THE 
TEATS IN a Dog, in two longitudinal rows con- ence on 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, z.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 
