THE (ESTRUS-PRODUCING HORMONE 99 



extraordinary hypertrophying power of an ovarian fragment, 

 sucfi criteria are very desirable. Castle and Phillips also state 

 that where ovarian regeneration takes place, the usual ovariec- 

 tomy effects are not found. Subsequently, Davenport (153), 

 working on mice, reported the results of an extensive series of 

 operations, most of which, however, were only unilateral. His 

 results show^ that regeneration is much more probable when 

 the ovary alone is removed, than where the capsule and Fal- 

 lopian tube are also excised. The percentage of regenerations 

 found by Davenport (given below) was remarkably high : — 



Davenport summarizes his results as follows: ' Regeneration of 

 the ovary in mice is less apt to occur when capsule, tube, and 

 part of the fat body are removed, than when the ovary alone is 

 removed by cutting its stalk and picking it out of the capsule 

 with least damage to the latter. Regeneration occurs equahy 

 in mice that were operated upon when only a month old and in 

 those which were three or four months old. Regeneration may 

 take place within a month or two after operation, but apparently 

 the proportion of regenerated mice increases until six months 

 have passed. Adhesions and minor infections do not inhibit the 

 reformation of the ovary, and such reformation is neither 

 facilitated nor inhibited by pregnancy (in case of unilateral 

 ovariectomy),' 



Clinical cases are also on record where pregnancy has occurred 

 in the human after the removal of both ovaries, though such 

 anomalies may be due to the presence of third ovaries. The 

 importance of this possibility of ovarian regeneration in the 

 testing of ovarian extracts has been indicated by Frank and 

 Goldberger (227). The improbability that new ovarian tissue 

 can arise after the removal of the original organs has always 

 fostered suspicion that the apparent regeneration is due to 

 the incomplete removal of the ovaries at the time of 



