102 



Scientific Proceedings (29). 



untried matings between parents having dissimilar characteristics. 

 The more highly developed condition dominates over the less 

 highly developed ; and in the extreme case the presence of a char- 

 acter dominates over its entire absence. This extreme case gives 

 results that accord with Mendel's law ; the cases in which the 

 characteristics of the parents differ merely in degree are often not 

 inherited* precisely in accordance with that law. 



60 (316) 



The experimental production of the maternal part of the 

 placenta in the rabbit. 1 



By LEO LOEB. 



[From the Laboratory of Experimental Pathology, University of 



Pennsylvania^ 



In a former communication 2 I stated that I had been able to 

 produce at will, decidual tumors in the uterus of the guinea-pig 

 by making deep incisions into the wall of the uterus, at certain 

 periods of the sexual cycle. The nodules thus produced belong 

 to that class of formations which I designated as " transitory 

 tumors." Since then, further investigations 3 have demonstrated 

 that these deciduomata are produced under the influence of an 

 internal secretion of the ovaries. There are indications that it is 

 the corpus luteum which produces this internal secretion. If such 

 a "preparing substance " has been secreted by the ovaries, indifferent 

 stimuli are sufficient to call forth the development of the deciduo- 

 mata. In the guinea-pig the new formations show a structure 

 identical with that of the decidua. Large cells of connective tissue 

 origin show an epithelial arrangement. The nuclei of many cells 

 are hypertrophic, the cytoplasm is, on the whole, solid, and stains 

 well with eosin. The decidual tissue of the placenta of the rabbit 

 differs in some important respects from that of the guinea-pig, if 

 we compare the placentas at the corresponding stages of develop- 

 ment. In the rabbit the decidual cells are quite vacuolar and the 



1 This investigation was carried out under a grant from the Rockefeller Institute for 

 Medical Research. 



2 Loeb : This journal, 1907, iv, p. 93. 



3 A report on these further investigations appeared in the Journal of the Ameri- 

 can Medical Association, June, 1908. 



