342 MINOT. [VoL. II. 
such a work, knowledge of the foetal envelopes seemed espe- 
cially important. I was thus led to examine them, and found 
in so doing that the structure of the parts differed in many re- 
spects from what had been assumed. The rabbit’s uterus was 
examined in the hope of obtaining light as to some of the 
changes in the human uterus, but the differences are so great 
that little help was gotten ; but on the other hand I was brought 
to a conception of the changes in the rabbit’s uterus so funda- 
mentally different from the views of previous writers that I was 
induced to carry my observations far enough to make sure of 
the essential alterations. The following communication is there- 
fore in no sense monographic, but only supplementary to the 
work of others. My own work has been accomplished by the 
aid of a grant from the American Association for the Advance- 
ment of Science, without which it could not have been carried 
out. The recipient of such aid naturally wishes to publish what 
he has accomplished, since such a publication is the most fitting 
acknowledgment of the assistance enjoyed. I feel my obliga- 
tions to the Association the more deeply because the grant is the 
first made from its Research Fund. May I express the hope 
that that fund will be largely increased, and the Association en- 
abled to make numerous grants to other workers, for in so doing 
it will do more for the promotion of science than, I believe, by 
any other means whatsoever. 
I. RABBIT. 
The observations here recorded were made upon pregnant 
uteri of the rabbit at various intervals from the sixth to the 
fifteenth day of gestation, both inclusive: The uteri were cut 
out carefully, stretched very slightly, and the ends of each uterus 
tied to an iron rod; the specimens were then hardened in 
Kleinenberg’s picrosulphuric acid, according to the directions 
given in Foster and Balfour’s Embryology, 2d ed. pp. 425, 426. 
Although this reagent worked fairly well, and preserved the 
histological elements of the uterus and of the older embryos 
satisfactorily, it failed to preserve the blastodermic vesicles in 
uteri of six and seven days; and in the older specimens, after 
hardening, the extra-embryonic foetal membranes were somewhat 
rumpled. Owing to the great difficulty of obtaining doe-rabbits 
