AUTHOR’S ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, FEBRUARY 27 
THE DEVELOPMENT OF. THE CLOACA IN BIRDS, 
WITH SPECIAL REFERENCE TO THE ORIGIN OF 
THE BURSA OF FABRICIUS, THE FORMATION OF A 
URODAEAL SINUS, AND THE REGULAR OCCUR- 
RENCE OF A CLOACAL FENESTRA 
EDWARD A. BOYDEN 
Department of Anatomy, Harvard Medical School 
FORTY-ONE FIGURES 
The cloaca of the domestic fowl has been an object of interest 
to anatomists since early in the seventeenth century. It was 
discovered by Hieronymus Fabricius while investigating the 
urogenital apparatus of birds in connection with his pioneer 
study of the chick embryo. In his posthumous treatise, entitled 
“De Formatione Ovi et Pulli,” Patavii, 1621, he describes as 
follows a blind sac lying behind the uterus of the fowl, but empty- 
ing into the cloaca close to its external orifice: 
A third thing to be noted in the anus is a duplex vesicle,! 
which in its deepest part rises up to the os pubis, and is seen 
clearly and further back as soon as the uterus, already described, 
offers itself to view. Since the vesicle is pervious to the extent 
that a passage opens below from the anus to.the uterus itself 
and from the uterus into the vesicle, as it were superiorly, the 
vesicle being closed at the other end, we have come to the belief 
1 The meaning of duplex in this passage is doubtful. The organ itself is never 
double. But in two species, a nestling raven (Osawa, 711) and the jay (Jolly, 715), 
it has been reported as bilobate. Osawa suggests that perhaps Fabricius may 
have had such a case before him when writing his description, but apparently 
Fabricius dealt only with the fowl, a species in which a bilobed condition has 
never been reported. The bursa is, however, two-walled, consisting of a mucous 
membrane and a muscular layer; and the recognized use of duplex to mean stout 
or thick, as applied to garments, may have been in the mind of Fabricius when he 
used this term. Unfortunately, its form is not recognizable in the woodcut in 
which he intended to show it. 
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