THE REPRODUCTIVE ORGANS 87 



this latter had been sensitized by the internal secretion of the 

 corpus luteum, the mechanical stimulation gave rise to a 

 maternal placenta an artificial deciduoma at the point of 

 stimulation. The mechanical stimulus has the same or a 

 very similar effect to that of the ovum. Even apart from 

 special mechanical stimuli, the uterine mucosa frequently 

 shows some slight deciduomatous growth, due in all probability 

 to some ill-defined stimuli occurring in normal life and rendered 

 effective by the internal secretion of the corpus luteum. 

 O'Donoghue finds that in marsupials, in which the yellow 

 body is persistent in the non-pregnant animal, the uterine 

 overgrowth is specially marked. He suggests that the effect 

 of the mechanical irritation is chiefly to localize the over- 

 growth, and thus produce definite deciduomata. 



Loeb's observations have been confirmed by several 

 authors. 



It seems clear, then, that the internal secretion of the corpus 

 luteum sensitizes the uterine mucous membrane and renders 

 it capable of reacting to mechanical stimulation. There is a 

 relation between the quantity of the internal secretion poured 

 out by the corpus luteum and the degree of response which 

 can be elicited by mechanical irritation. The .response can 

 only be obtained when an amount of secretion sufficient to 

 sensitize the mucous membrane has been poured out. If the 

 stimulus be applied when the body is just beginning to secrete, 

 little effect may be produced. But if the stimulation is 

 carried out later on, at a time when the uterine mucous mem- 

 brane has become completely sensitized, the secretion of 

 the substance goes on for a few more days and increases the 

 reaction. The ovum becomes attached at about the time when 

 the greatest sensitization of the mucosa has been obtained. 

 The substance secreted by the yellow body is not specific, that 

 is to say, the substance secreted by one individual will cause 

 growth in the sensitized uterus of a second individual of the 

 same species. The effect, however, is less pronounced than 

 in the organism to which it belonged. This difference is 

 supposed to be due to the presence of " homoiotoxins " in 

 the second individual. The artificial deciduomata in any 

 particular species have the structure of the normal maternal 

 placenta. In some animals these are confined to the uterus, 

 but in women deciduomata can be produced in the Fallopian 



