126 DELLA DRIPS 
1912 most of the papers written were reports of experimental 
studies undertaken to prove that the corpus luteum is the gland 
of internal secretion in the ovaries, and that, through this 
secretion, the luteal structure produces specific effects on other 
organs, particularly the uterus. In spite of the many criticisms . 
directed against his work, Fraenkel still stands preéminent 
among the experimental workers who established beyond a doubt 
the foregoing hypothesis. 
Since 1910, efforts have been put forth by investigators actually 
to demonstrate this secretion in the corpus luteum. Van der 
Stricht comes nearer the goal than any others. The greater 
part of recent literature, however, concerns the extract of the 
corpus luteum, its chemical constituency, its physiologic action, 
and its clinical value. . 
THE OVARIAN CYCLE 
In the summer of 1914, while studying microscopic sections of 
the various tissues and organs of the spermophile, the relatively 
immense size of the ovaries, compared with those observed the 
previous spring, strikingly presented itself. On further compari- 
son, it was very evident that this great increase in size had been 
brought about by a growth in the corpora lutea only. One 
ovary contained eleven of these bodies; there remained only 
a framework of ovarian stroma with a few atretic follicles. 
With the particular: stain the luteal cells bore a marked re- 
semblance to the cells of the cortex of the adrenal. The former 
- were much larger, but the shape of both, their arrangement in 
columns, the position and appearance of the nuclei, and the 
presence of lipoid droplets in the protoplasm accounted for the 
likenesses. In fact, the luteal cells resemble secreting cells. 
From observations that had been going on, it was known that 
these spermophiles had given birth to young about a month 
before. According to most writers, degeneration of the luteal 
cells begins not later than birth. Here were what looked like 
actively secreting cells a month after birth. ‘Thereupon it was 
decided to try out some differential stains on these luteal cells 
at every stage in their life history, and to study the complete 
