B I R 



B I R 



laterally, and are diftributed to the neighbouring parts, and 

 to the kidnies and ovidutl ; the third branch defcends to the 

 very point of the tail, upon the mufcles and quills of whicli 

 its branches are exhaullcd. 



The arterial fy'lem of birds diffVrs from that of other 

 animals chiefly in the frequent anallomofes, which exift more 

 efp^cially amongft the arteries of the head and the vifctra. 

 Similar communications occur between the veins, which are 

 even in fome inftances more fingular and unaccountable, as 

 will be peiceived by the following defcription, which has 

 been takea principally from the goofe, duck, and common 

 fotul. 



Veins. 



The venous fydem returns the blood to the heart by 

 means of three trunks ; two of thefe, for the convenience 

 of defcription, we fhall call the fubclavian veins, although 

 they do not correfpond in every refpecl with the veins of 

 this name in mammalia ; the other trunk is analogous to the 

 inferior vena cava. 



Tht fubclavian vein is compofed of the jugular and verte- 

 bral, and the veins which belong to the fuperior extremity or 

 wing. 



The vertebral vein is lodged in the fame canal with the 

 Tertebral artery ; it anaftomofes between the vertebrx with 

 the veins upon the fl'.eath of the medulla fpmahs, which are 

 the continuation of the linufes of the brain ; in conjunction 

 with thefe, therefore, the vertebral vein may be confidered 

 ai anfwering the purpofe of the internal jugular of mamma- 

 lia. It appears alfo to form at the bafis of the cranium a 

 free communication with the jugular vein, and to receive 

 by occafional branches, blood from the mufcles of the 

 neck. 



The jugular vein is a fingle trunk in birds, and does not 

 admit of the dillinftion into external and internal ; it pro- 

 ceeds fuperficially along the fide of the neck in company with 

 the par vagum nerve. The vein of the right iide exceeds the 

 other in fize ; it is often twice as large. The jugular 

 vein receives feveral lateral branches from the mufcles and 

 integuments of the neck, the oefophagus, &c. ; one of 

 thefe near the head is much larger than the reft: ; it lies deep 

 amongft the mufcles, and appears to communicate with the 

 vertebral vein. There is a branch of the jugular which goes 

 amongft the mufcles of the tongue and of the os hyoides, 

 and another for the mufcles within the jaws and the integu- 

 ments in the back of the mouth ; thefe might be called 

 the lingual anA fubmaxillury veins. 



The two jugular veins form a moft remarkable communi- 

 cation with each other immediately below the cranium, by 

 means of a crofs branch, generally of an equal fize with the 

 trunks themfelves. From each fide of the arch thus formed 

 there ifliies a large vefTel, which is made up of the veins 

 of the external part of the head ; one of thefe pafies round 

 the articular bene, and apparently penetrates the joint of 

 that bone with the lower jaw ; it appears in feveral 

 branches upon the fide of the cheek, and fpreading from 

 the ear, in the manner of the portio dura nerve of the hu- 

 man fubjetl, and contributes to form a plexus of veins below 

 the pofterior part of the orbit, fimilar to tlie arterial pkxus 

 already defcribed in that fituation. The principal branch of 

 the veins of the head pafies obliquely ruund the inter-articu- 

 lar bone, and below the orbit divides into feveral large vef- 

 fels ; one of which belongs to the back part of the palate ; 

 another afcends in the orbit, and unites with the ophthal- 

 mic vein ; and a third is dillributed to the interior of the 

 organ of fmell, the palate, and the external parts of the up- 

 per and lower jaws. Thefe branches produce plexufes along 

 the bafe of the orbit and the external edge of the palate, 



which correfpond to thofe cf the arteries before de- 

 fcribed. 



In all the fubjcfts we difTcfted .''or the veins we failed to 

 difcover any dircft communication between the jugular vein 

 and the finufes of the brain ; and in every inftance the ex- 

 ternal veins of the head appeared to be fufficieiitly large of 

 themfelvcs to produce the trunk of the jugular. It may 

 therefore be prefumed, that if any branch analogous to the 

 internal jugular vein pafifes through the pofterior foramen 

 lacerum, it is veiy inconfiderable, and incapable of tranf- 

 mitting the blood of the brain. 



The finufes of the bruin feem to difcharge their contents 

 principally into fome veins, which lie in the membrane 

 forming the ftiealh of the fpinal canal, and thefe appear to 

 difpofc of their blood gradually, as they defcend in the 

 neck, by means of lateral communication with the vertebral 

 veins. The finufes, which immediately open into the fpinal 

 veins, are fituated upon the back of the cerebellum, and 

 produce by anaftomofes with each other, with the fuperior 

 longitudinal finus, and with others along the fides of the 

 brain, an union of vefiels, of a diamond fiiape. 



The finufes of the brain in birds generally are irregular 

 in their form, and confift of flattened canals ; and not only 

 the finufes on the back of the cerebellum, but the fpinal 

 veins appear fo like extravafation, that accurate and repeat- 

 ed obfervations are neceflary to difcover them to be real 

 vefiVls. 



The principal finufes, befides thofe upon the cerebellum, 

 are the fuperior longitudinal, and one whieh runs along the 

 lower edge of each hemifphere of the cerebrum ; there ap- 

 pears to be alfo one upon the fide of the cerebellum, cor- 

 relponding to the lateral finiis. All the finufes communi- 

 cate with each other on the back of the cerebellum as al- 

 ready mentioned. The fuperior longitudinal finus is con- 

 tmued at its anterior part ur.dcr the frontal and nafal bones, 

 and anaftomofes with the ophthalmic and nafal veins. There 

 arc other finufes in the ieveral duplicatures of the dura ma- 

 ter, which are too fraall to be ealily traced, or to dcferve 

 much regard. 



The veins of the luing, or fuperior extremity, have a lefs 

 curious diftribution than thofe of the head. The branches 

 which are derived from the parts within the cheft, the muf- 

 cles about the fcapula, and the peftonil mufcles, accompany 

 the arteries of the fame parts, fo regularly that their courle 

 does not require defcription. 



The vein lies confiderably lower in the axilla than the ar- 

 tery, but ftill continues to receive correfponding branches. 

 The trunk of the vein defcends in the courfe of the hume- 

 ral artery, but more fuperficially ; in this fituation it may 

 be called the bafiUc, or more properly the humeral., vein. 

 There is no vein in birds which delerves the name of the ce- 

 phalic ; there are branches of the humeral vein, accompany- 

 ing the articular and profunda arteries, and at the middle 

 of the humerus, a large branch of the vein enters the bone ; 

 there are alfo two very fmall branches which lie in clofe coa- 

 taii with the humeral artery, which they accompany nearly 

 its whole length. 



The principal vein of the wing divides into two, oppofite 

 to the joint of the humerus with the fore arm. One of thcle 

 branches belongs to the fides of the radius ; it receives blood 

 from the mufcles and fkin on the upper part of the fore arm, 

 but its chief veffcls lie between the integuments of the fold 

 of the wing. The other branch of the humeral vein crofles 

 the fore arm, juft below the articulation, in company with 

 the nerve, and running along the inferior edge ot the ulna, 

 receives a branch from between the bafis of each quill, is 

 continued along the ligament which fudains the reft of 



the 



