162 
J. P. HILL AND CHAS. H. o’dOHOGHUE. 
Pregnancy. — Fertilisation is effected in the upper part 
of the Fallopian tube and the second polar body is there 
given off. 
As a rule more young are born than can possibly survive 
owing to the limited accommodation in the pouch. 
The gestation period is not less than eight and not 
more than fourteen days, but the interval between copulation 
and birth is usually considerably longer. 
Corpora lutea are formed and persist throughout the greater 
part of the time that the animal is lactating. 
Nursing Period. — This period may be divided into two 
phases. 
(1) Period of Fixation. — A period, lasting for seven or 
eight weeks, during which the young are firmly attached to 
the teats. 
(2) Free Period. — A period of eight or nine weeks when 
the young are free in the pouch but dependent on the mother 
for food. 
After this time the various organs gradually return to a 
state of rest. 
Pseudo-pregnancy. — We have applied this term to the 
period following ovulation in cases where the ova have failed 
to develop, because of the occurrence in it of a series of 
changes in the reproductive organs essentially identical with 
those met with in pregnant females. 
Corpora lutea are formed in the ovaries which are identical 
with those in the pregnant female. 
The pouch enlarges, and its sweat and sebaceous glands 
reach a state of hypertrophy and functional activity com- 
parable to that in the pregnant female. 
The mammary glands also enlarge and reach a state of 
development equal to that in a female thirty-six hours after 
parturition. 
The uteri enlarge and become vascular, often to a marked 
degree. 
The uterine mucosa undergoes a series of changes, pro- 
gressive, regressive and regenerative. 
