THE DEVELOPMENT OF THE CORPUS LUTEUM. 193 
of an experimental inquiry upon the formation of the corpus 
luteum in the sheep. In this inquiry the sheep were killed 
at stated periods either after coition or after the animals had 
been observed to undergo cestrus. The relation which was 
found to exist between the condition of development of the 
corpus luteum and the length of the interval that was allowed 
to elapse between cestrus and the killing of the animal, was in 
itself a strong presumption that ovulation in the sheep occurs 
normally during cestrus. Thus the approximate age of the 
young corpus luteum or discharged follicle could in every 
case be determined. The result of this investigation was to 
confirm in all essential particulars Bischoff’s theory, which 
had been accepted by Sobotta. The sheep, however, was 
found to present some differences from the mouse in regard 
to the mode of formation of the corpus luteum, the connective 
tissueingrowth being derived partly from the thecaexterna, and 
not merely from the theca interna, and the follicular epithelium 
continuing to undergo division after the rupture of the follicle, 
but with greatly decreased frequency. The former of these 
two observations is in agreement with Honoré’s statement in 
regard to the interepithelial connective tissue in the rabbit. 
The theca interna was said to become entirely used up in the 
formation of the connective-tissue ingrowth, this statement 
agreeing with Sobotta’s description, but differing from that 
of Honoré. Two years later the complete account of the 
development of the corpus luteum in the sheep was published. 
The description given in these papers is thus completely 
opposed to His’s suggestion that the mode of formation of 
the corpus luteum in the larger mammals is different from 
what it is in small animals like the mouse and rabbit, unless, 
as Sobotta remarks, it was intended to include only the ele- 
phant and the whale in the former category. 
Meanwhile, in 1901, the same year in which the preliminary 
account referred to above was issued, van der Stricht pub- 
lished descriptions of the developing corpus luteum of bats 
belonging to the genera Vesperugo, Vespertilio, and 
Placotus. This author’s researches also resulted in con- 
