118 DELLA DRIPS 
from the internal theca of the follicle according to the hypoth- 
’ esis of von Baer, or were they epithelial in nature and derived 
from the membrana granulosa of the follicle as advocated by 
Bischoff? Marshall, in his book, ‘‘The Physiology of Repro- 
duction” (’10), carefully reviews this early literature. 
It was not until Sobotta (96) published the first of his series 
of papers on the corpus luteum that the discussion over the origin 
of the luteal cells began to come to an end. Sobotta’s study on 
the corpus luteum of the mouse was the first systematic record 
of the transformation of the follicle into a corpus luteum and 
the latter’s subsequent development. He describes, first, the 
follicle about to burst; then, one just after bursting; one, one-half 
hour afterward, and others at succeeding short intervals up to 
seventy-two hours after bursting. All the descriptions are very 
detailed, every change in the structure as it proceeds in its de- 
velopment being noted. Sobotta traces the origin of the luteal 
cells to the epithelial cells of the granulosa of the follicle. The 
internal theca cells, he says, expend themselves utterly in the 
formation of connective tissue and blood-vessels. The external 
theca remains as it was. 
‘Sobotta believed the function of the corpora lutea was to 
maintain a constant equal tension in the ovaries, which shows 
how little thought he gave to this phase of the problem. He was 
all absorbed in the formation of the luteal structure. This paper 
of Sobotta’s was followed shortly by a very similar one on the 
rabbit, in which he confirmed all of his findings in the mouse. 
These papers started a real investigation of the corpus luteum, 
and for the following ten or fifteen years there were any number 
of papers written regarding it. A few writers continued the 
discussion as to the origin of the luteal cells. Some criticised 
Sobotta, trying to disprove his statements. Among these was 
Clarke (’98), who contributed an account of the formation of the 
corpus luteum in thesow. His studies were made on serial sections 
of pig’s corpora lutea and follicles in different but not subsequent 
stages of development. The sections in each set were treated 
alternately to a process of tryptic digestion and a picro-fuchsin 
stain. From a study of these sections he concludes that the 
