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side the pericardium^ certain fine hands of fibrous tissue, which descend 

 beneath the pleura, from the trunk of the left superior intercostal 

 vein to the front of the root of the left lung ; and inside the peri- 

 cardium, a fold of the serous membrane which passes down from the 

 left pulmonarv artery to the subjacent pulmonary vein, — certain 

 opaque lines or streaks upon the side and back of the left auricle, — 

 a small oblique auricular vein whicli is continued from those streaks 

 down to the coronary sinus, — and lastly, the coronary sinus itself. 

 The fold of the pericardium, which hitherto has escaped observation, 

 is particularly described. It is named by the author the vestigial 

 fold of the pericardium, or, from its having contained the canal of 

 Cuvier in the embryo, the Cuvierian fold. 



2. Under the second head, a comparison is instituted between the 

 great anterior veins of Man and the Mammalia generally. 



Having remarked that, as high up in the vertebrate scale as Birds, 

 no fundamental alteration occurs from the primitive condition of two 

 anterior and two posterior independent lateral venous trunks, the 

 author remarks that in all Mammalia one characteristic change is 

 met with, viz. the formation of a transverse branch across the root of 

 the neck. 



The right anterior primitive vein in all cases persists as the right 

 or ordinary vena cava superior ; but the left vein either remains un- 

 occluded, and returns the blood from the left side of the head and 

 neck, from the left upper limb, the left side of the thorax, and from 

 the substance of the heart; or, owing to a partial occlusion, returns 

 only the blood from the left side of the thorax and from the substance 

 of the heart ; or, owing to still further occlusion, from the substance 

 of the heart alone. Hence three principal groups arise. 



a. In the first group a right and a left superior vena cava exist, 

 connected by a cross branch at the root of the neck, as in the Mono- 

 tremata, Marsupialia, the Elephant, most Rodentia, the Hedgehog 

 and the Bat. 



b. In another group a right superior cava and a left vena azygos 

 exist, as in the Sheep, Goat, Ox, Pig, Horse, Mole and Guinea Pig. 



c. In the third group there is found, besides the right vena cava 

 superior, only a left cardiac venous trunk or coronary sinus, together 

 with the vestiges already described, as in the Cetacea, Carnivora and 

 Quadrumaua, as well as in Man. 



In each of these groups subordinate varieties are shovrn and clas- 

 sified. 



3. Uie almost numberless varieties of the great anterior veiiis i?i the 

 human subject are then arranged on principles similar to those adopted 

 in regard to the diff'erent conditions found among Mammalia ; but 

 the groups are arranged in the inverse order, and the usual con- 

 dition of the veins in ^lan is included as a necessary element in the 

 series. 



In one large class of cases, comprehending three groups similar to 

 those of the different Mammalia already defined, the cross branch in 

 the neck is always present. 



a. In the first group there is a right vena cava superior, and a left 



