86 
BRITISH ASSOCIATION.- 1835. 
open state ; while, again, there being two bones connected by liga¬ 
ment, the elasticity of the vessel is not impaired. These bones, 
moreover, serve to support the septum of the auricles, and to prevent 
their perfect closure or collapse, and they also floor and support two 
of the aortic sinuses with their semilunar valves. The Professor 
next spoke of the peculiar, hard, marble-like fat which is deposited 
in masses about the roots of the great arteries, and showed that these 
cover the three sinuses of the pulmonary artery, and that sinus of the 
aorta which is deprived of osseous support. These arterial sinuses 
are lodged in excavations in the fatty deposits alluded to, and no 
ordinary force can overcome the resistance which they offer to over¬ 
distension ; and thus the sinuses are enabled to support the returning 
columns of blood, which are impelled by the elasticity or resiliency 
of the arteries, which in such animals are peculiarly strong and elastic. 
The author next explained the structure and true use of the corpora 
Arantii; contrasted the structure of the pulmonary artery and its 
valves with the corresponding parts of the aorta; and concluded 
with some observations on the calcareous and osseous deposits which 
are met with in the human subject, in whom they appear as acci¬ 
dental or morbid changes in those very situations where in some 
animals the osseous structure is essential. 
On the Structure of the Mammary Glands in the Cetacea; with Ob¬ 
servations on the Mechanism of the Mouth and Soft Palate , as ap¬ 
plied by the young Animal in Sucking. By A. Jacob, J/.Z1., 
Professor of Anatomy, Royal College of Surgeons , Ireland. 
The author, commenting on the opinions of M. Geoffroy St. Hilaire 
in his work entitled “ Fragmens sur la Structure et les Usages des 
Glandes mammaires des Cetaces,” and referring to the descriptions 
of Hunter and plates of Muller, entered into the question of the 
mechanism of the mammary glands in Cetacea, and the operation of 
the mouth of the young of that tribe. 
M. St. Hilaire is stated by the author to entertain the opinion that 
“ the process of nutrition of the young of the Cetacea by the milk of 
the mother, is accomplished in a manner and under circumstances 
different from those of other mammalia;’ To support this proposi¬ 
tion, M. St. Hilaire assumes that the mammary glands in these ani¬ 
mals are peculiarly organized and circumstanced; first, in being 
placed between the abdominal and subcutaneous muscles, by which 
they are subjected to mechanical pressure adequate to the expulsion 
of their contents; and secondly, in containing a peculiar reservoir, 
formed by an enlargement of the excretory ducts, and running the 
whole length of the organ. 
These statements are admitted by Dr. Jacob; but he remarks, 
that there is no proof of any special pressure on the mammary gland 
arising from its position with reference to the muscles; and that the 
only peculiarity in the excretory ducts is the existence of the mam¬ 
mary reservoir, in the form of a single cavity,—a circumstance which 
