AVES. 



339 



sheath of the medulla spinalis, which are the 

 continuation of the sinuses of the brain ; in 

 conjunction with these, therefore, the vertebral 

 vein may be considered as answering the pur- 

 pose of the internal jugular of mammalia. It 

 appears also to form at the basis of the cranium 

 a free communication with the jugular vein, 

 and to receive, by occasional branches, blood 

 from the muscles of the neck. 



" The jugular vein (b) is a single trunk in 

 birds, and does not admit of the distinction 

 into external and internal ; it proceeds super- 

 ficially along the side of the neck in company 

 with the par vagum nerve. The vein of the 

 right side exceeds the other in size ; it is often 

 twice as large. The jugular vein receives several 

 lateral branches from the muscles and integu- 

 ments of the neck (d), the oesophagus, &c. (the 

 veins from the crop joining the jugular are 

 shewn at c): one of these near the head is 

 much longer than the rest (e); it lies deep 

 amongst the muscles, and appears to com- 

 municate with the vertebral vein. There is a 

 branch of the jugular which goes to the supe- 

 rior larynx amongst the muscles of the tongue 

 and of the os hyoides, and another for the 

 muscles within the jaws and the integuments 

 in the back of the mouth ; these might be 

 called the lingual, thyroid, and submaxillary 

 veins (g h i). 



" The jugular veins form a most remarkable 

 communication with each other immediately 

 below the cranium, by means of a cross 

 branch, generally of an equal size with the 

 trunks themselves. From each side of the 

 arch thus formed there issues a large vessel, 

 which is made up of the veins of the external 

 part of the head ; one of these passes round 

 the articular bone, and apparently penetrates 

 the joint of that bone with the lower jaw ; it 

 appears in several branches upon the side of 

 the cheek, and spreading from the ear in the 

 manner of the portio dura nerve of the human 

 subject, and contributes to form a plexus of 

 veins below the posterior part of the orbit (/c), 

 similar to the arterial plexus already described in 

 thatsituation. The principal branch of the veins of 

 the head passes obliquely round the interarticular 

 (or pterygoid) bone, and below the orbit divides 

 into several large vessels, one of which belongs 

 to the back part of the palate ; another ascends 

 on the orbit, and unites with the ophthalmic 

 vein ; and a third is distributed to the interior 

 of the organ of smell, the palate, and the 

 external parts of the upper and lower jaws. 

 These branches produce plexuses along the 

 base of the orbit and the external edge of the 

 palate, which correspond to those of the arte- 

 ries before described. 



' In all the subjects we dissected for the veins, 

 we failed to discover any direct communication 

 between the jugular vein and the sinuses of 

 the brain ; and in every instance the external 

 veins of the head appeared to be sufficiently 

 large of themselves to produce the trunk of 

 the jugular. It may, therefore, be presumed 

 that if any branch analogous to the internal 

 jugular vein passes through the posterior fora- 

 men lacerum, it is very inconsiderable, and 



incapable of transmitting the blood of the 

 brain. 



" The sinuses of the brain seem to discharge 

 their contents principally into some veins 

 which lie in the membrane forming the sheath 

 of the spinal canal, and these appear to dispose 

 of their blood gradually, as they descend in 

 the neck by means of lateral communication 

 with the vertebral veins. The sinuses, which 

 immediately open into the spinal veins, are 

 situated upon the back of the cerebellum, and 

 produce, by anastomoses with each other, with 

 the superior longitudinal sinus, and with others 

 along the side of the brain, an union of vessels 

 of a diamond shape. 



" The sinuses of the brain in birds generally 

 are irregular in their form, and consist of flat- 

 tened canals; and not only the sinuses on the 

 back of the cerebellum, but the spinal veins 

 appear so like extravasation, that accurate and 

 repeated observations are necessary to discover 

 them to be real vessels. 



" The principal sinuses, besides those upon 

 the cerebellum, are the superior longitudinal, 

 and one which runs along the lower edge of each 

 hemisphere of the cerebrum ; there appears to 

 be also one upon the side of the cerebellum, 

 corresponding to the lateral sinus. All these 

 sinuses communicate with each other on the 

 back of the cerebellum as already mentioned. 

 The superior longitudinal sinus is continued at 

 its anterior part under the frontal and nasal 

 bones, and anastomoses with the ophthalmic 

 arid nasal veins. There are other sinuses in 

 the several duplicatures of the dura mater, 

 which are too small to be easily traced or to 

 deserve much regard. 



" The veins of the wings, or superior ex- 

 tremity, have a less curious distribution than 

 those of the head. The branches which are 

 derived from the parts within the chest, the 

 muscles about the scapula, and the pectoral 

 muscles, accompany the arteries of the same 

 parts so regularly that their course does not 

 require description. 



" The axillary vein (F) lies considerably 

 lower in the axilla than the artery, but still 

 continues to receive corresponding branches; 

 (m indicates the great pectoral vein). The 

 trunk of the vein descends in the course of the 

 humeral artery, but more superficially; in this 

 situation it may be called basilic, or more pro- 

 perly the humeral, vein (). There is no vein 

 in birds which deserves the name of the ce- 

 phalic; there are branches of the humeral vein, 

 accompanying the articular and profunda arte- 

 ries, and at the middle of the humerus a large 

 branch of the vein enters the bone ; there are 

 also two very small branches which lie in close 

 contact with the humeral artery, which they 

 accompany nearly its whole length. 



" The principal vein of the wing divides into 

 two, opposite to the joint of the humerus with 

 the fore-arm. One of these branches (o) belongs 

 to the sides of the radius ; it receives blood 

 from the muscles and skin on the upper part 

 of the fore-arm, but its chief vessels lie be- 

 tween the integuments of the fold of the wing. 

 The other branch of the humeral vein (p) crosses 



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