lof) IXIKODIU'IION I'O Sl'.XUAL IMIVSIOLOCiV 



and llic piciiu'iisl iiial iilcrns is said Jo imdcrjijo clianfijcs similar 

 1(» tliosc of the |)r('<jjnaiit ()i-«i;an, and it is prohahic tliat tliese 

 also dcpt'iid upon 1 lie coipus hitciim. (\)riu'r lias describtMl 

 (•oin|)aral)l(' changes in monkeys, hul only il ovulation had 

 occuncd |)i'('\iously. 



Decidual cells are not normally formed in the uterine mucosa 

 e.\ce()l iuii; in true pre^jcnancy, hut as was first shown by Leo Loeh 

 in the i;uinea-|)iii;, nodules composed of decidual tissue ca.n he 

 induced to develop as a result of direct stimuli to the mucosa, 

 sucli as the introduction of a. foreign body or the makinjj!; of 

 incisions in the nuicosa. The nodules which Ivoeb describes 

 muler the term " deciduomata, " arise through the proliferation of 

 the int(M--gla.ndular connective tissue. They can be induced to 

 form most readily from the third or fourth to the eighth or ninth 

 days after heat, and therefore at a time when freshly formed 

 and active corpora, lutea are |)resent in the ovaries, 'i'he formation 

 of decidual tissue was not caused by ova. in the uterus, since it 

 took place when that organ was ligatured oil" so as to prevent 

 the |)assag(^ of the ova. If, however, the ovaries with their con- 

 tained coi'poi'a lutca ar<> extirpated, deciduomata. are not 

 pi'oduced. On the other hand, if pieces of uterine nuicosa. are 

 traiis|)lante(l into subcuta.neous tissue (hn-idual nodules are 

 formed in the grafted tissue. l--oeb concludes, therefore, that 

 for a certain interval after ovulation the corpora, lutea elaborate 

 a predisposing substance in the presence of which indilVerent 

 stinudi may produc(> the formation of deciduomata. 



llanunond has shown further that placental tissue may be 

 formed in the uterine nuicosa of the rabbit by similar methods, 

 but oidy during an experimentally induced pseudo-pregnancy. 

 Such a formation of decidual tissue is clearly comparable to that 

 ])roduced during true pregnancy when corpora lutea are normally 

 ])i-i'sent i!i tlu^ ovaries. 



Long and l<]vans state that in the rat, owing to the short 

 " dicpstrum" and the corresponding abbreviation in the duration 

 of the "corpus luteum sj)urium " or "corpus luteum of ovula- 

 tion,"' deciduomata cannot be induced in the uterine mucosa, 

 if, however, the female rat undergoes a sterile coition with a 

 vasectomised male the corpus luteum persists for a longer period 

 and tlie subsequent oestrus is postponed. This is believed to 

 be due to the formation of the vaginal plug which extends into 



