GROWTH-CHANGES IN MAMMARY APPARATUS OF DASYURUS. 233 
( fol .). Note the absence of hair from the other parts of the skin. The 
secondary or sebaceous outgrowth ( seb .) and the tertiary or mammary 
outgrowth (ter.) are also shown, and the latter is cut again in its tubular 
part ( t .) 
Fig. 2. — Photo-micrograpli ( X about 16). Transverse section of teat 
and gland in the adult resting pouch (i . e . Series 3) . 
Fig. 3. — Photo-micrograph ( X about 16). Transverse section of teat 
and gland just before attachment of embryos to uterus (i. e. Series 14). 
It shows the maximum development of the sebaceous glands (seb.) and 
at the base of the section a portion of the cremaster muscle (c.m.). 
Fig. 4. — Photo-micrograpli ( X about 16). — Transverse section of teat 
and gland just before the birth of the young (i.e. Series 17). Com- 
parison with fig. 3 shows that the sebaceous (seb.) and sweat-glands (sw.) 
are no further advanced, while the mammary glands have enlarged. 
Fig. 5. — Photo-micrograpli (x about 16). Transverse section of teat 
and gland with new-born young in the pouch (i.e. Series 18). The 
state of the mammary glands is practically the same as in fig. 4. It 
also shows a part of the lymph-gland ( l .), which underlies the mammary 
gland and is more enlarged here than in the resting pouch. 
Fig. 6.— Photo-micrograpli (x about 16). Transverse section of teat 
and gland at the commencement of milk flow (i.e. Series 21). Owing 
to the way in which the teat was bent upon itself the section runs 
nearly transversely across it, and so shows clearly the six main ducts (d.) 
which open separately on its surface. 
Fig. 7. — Photo-micrograph ( X about 16). Transverse section of teat 
and gland when the young are thirty-four days old (i.e. Series 23). 
The ducts (d.) are dilated with milk (m.c.), as the animal was probably 
killed while feeding her young. The opening of two milk-ducts (d. o.) 
appear on the surface of the teat. 
Fig. 8. — Photo-micrograph (x about 16). Transverse section of part 
of the mammary gland in full activity when the young are four months 
old (i.e. Series 25). This is magnified to the same extent as figs. 2-7, 
and shows the enormous hypertrophy undergone by the gland. The 
alveolar walls (w.) are reduced to mere lines. 
Fig. 9. — Photo-micrograpli ( x about 16). Transverse section of teat 
and gland where ovulation has not been followed by pregnancy (Series 
27.) Note the advanced state of the gland, it is more advanced than 
that in fig. 3. 
Fig. 10. — Photo-micrograpli ( X about 16). Transverse section of teat 
and gland where ovulation has not been followed by pregnancy (Series 
30). Comparison will show that the gland is in a more advanced state 
than any of those before parturition, and it corresponds|most nearly to 
that in fig. 6. 
