340 EDGAR ALLEN 
3. Do they exert a destructive influence on the mucosa of the 
genital tract? Frankel (’03) attempted to prove that the cor- 
pus luteum by means of an internal secretion exerted a destruc- 
tive influence on the uterus. Although newly forming corpora 
lutea are present during the metoestrum in the ovaries of mice 
which ovulate spontaneously, in those which do not, none need 
be present. And yet typical metoestrous degenerative changes 
in the genital tract occur. Consequently, the corpora lutea can 
hardly be considered as the cause of cyclical degeneration. 
4, Do the corpora lutea furnish a growth stimulus? Stock- 
ard and Papanicolaou think it probable that the corpora lutea 
of oestrus exert a protective influence on the uterine and vag- 
inal mucosae, because they find well-developed corpora present 
during the stages in which no degenerative changes are apparent 
in these organs, and because corpora of oestrus begin to retro- 
gress before the next metoestrum sets in. They write: ‘The 
facts obtained in the present investigation might not fully war- 
rant the position that the corpus luteum really exerted an active 
protective influence over the uterine mucosa, but they certainly 
in no sense suggest, and actually speak against, any injurious 
action on the mucosa by the secretion of the corpus luteum.” 
This may be taken as a constructive suggestion to combat Fran- 
kel’s views. That the corpora lutea are not the principal factors 
in the growth phase of the genital tract during the prooestrum 
in the mouse is plain for two reasons: 1) In those animals 
where spontaneous ovulation is the rule and where two or three 
sets of large corpora are always present, these degenerative 
changes occur just the same. 2) In animals that never have 
ovulated spontaneously, and where consequently no corpora are 
present in the ovaries, the same regenerative growth processes 
occur. Consequently, Stockard and Papanicolaou’s explana- 
tion of growth under the protective influence of a secretion from 
the corpora lutea is hardly applicable to the mouse. 
Therefore, evidence from the mouse brings strongly into ques- 
tion the value of corpora lutea of oestrus, 1) as inhibitors of 
ovulation, 2) as sources of destructive hormonal influence, or, 
3) of endocrine growth stimulus exerted on the uterus. 
