Section of Medical Science. 507 



osseous nuclei were distinct in the cartilaginous basis. The author 

 next adverted to the peculiar fleshy character of the left ventricle in 

 the ox, a transverse section exhibiting the appearance of a puncture 

 or stab, rather than of a distinct chamber ; this formed a curious 

 contrast to the heart of the horse. From these and many other ob- 

 servations, Mr. Harrison inferred that these bones are supports, not 

 only to this mass of muscle, but also to the root of the aorta which 

 is connected to th,em, and which is thus maintained in a permanently 

 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, M.I)., 

 Professor of Anatomy, Royal College of Surgeons, Ireland. 



The author, commenting on the opinions of M. G. 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, 



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