I t has I)een cleiiionstratetl that the clinical ~y i 1 1 1 ) t o i i i "interiiienstriial 1)aiii'' (11 ittelsclinicrz) ol)scrvctl in \voiiieii is I)rotlucetl 1)y v;irious ~~l~y s i o~~~i t l~o l o g i c~i l I)rocesses \vIiicli titkc place eitlicr in the o v a r y or in the uterus. 1Iyperenii;i in the entlometriuni, for instance, may IK ;iccoiiil);iiiietl 1)y ;I slight I)lootly f l o w \vIiicli occ;ision;illy conforms to ;i sc;itity -*menstrual flow" atitl occurs ;ilq)roxitnately in the mid-interval o f the iiiciistrual cycle. 1 t may o r inay not I)e ;iccoiiil);iiiietl l)y Inin. 'I'his syiiil)toiii h;is also I)ceii ol)scrvetl on certain s1)ecies of nioiikcy. 1 i ; i r t e l n i c z (1()41)1 tlre\v a tlistiiictioii I)et\\-ecii this ty1)e of I)!eetliiig ;ind true iiieiistrual flo\\-, ant1 I)lcctliiig ;it the time of iiitlation, ant1 termed it *.l)reovul;itory I)leetliii~ associated with 1iyl)ereiiiia". I le \\-rote that it \\-as "rather uiicotiii~ioi~'*.1 lie characteristical feature of this type o f h;iemorrhage is that i t oriKiiiates froin a proliferative cri(lometriurn conforining thus to bbanovul;itory menstruatioii". I< o c k , I$ a r t I e t t and 11 a t s o 11 18 rel)orted that it occurred occasioiially ((1. I I)er cent) in 392 \vomeii \vho sought inet1ic:il advice for sterility. 'I'hey wrote that, in contrast t o "l)reoviilatory I)leecling" \\-hich occurs always in the iiii(l-iiitervaI, *.;inovul;itory iiienstru;itioii" may occur ;it tlifferent times (luring the cycle. 1 Ience, I)lc.etliiig from a proliferative ciitloinetriuiii at the time o f an expected Iwriotl may occur also in patients whose menstrtial cycle is regular.*.