NERVOUS SYSTEM. VERTEBRATA. !>.', 



Blood-vessels of the Brain. 



D. 741. The head of a Dog-fish (Acanthias vuljaris] .)., win-. 

 from the ventral surface, the arteries of the brain and their 

 connection with the carotids. Two carotid uteri 

 either side from the efferent vessel of the first dcmil.nmrli 

 an anterior carotid or hyoidean artery and a posterior 

 carotid. The posterior carotid divides at the hinder honh-r 

 of the orbit into an external and an internal trunk ; tin 

 latter enters the cranial cavity and passes across it in tin- 

 perichondrium below the hypophysis, to form a connection 

 with the internal branch of the opposite hyoidean ar 

 The hyoidean artery gives off in the orbit an external 

 (ophthalmic) and an internal branch. The latter divid-> 

 into (i.) the above-mentioned connection with the posterior 

 carotid artery, and (ii.) a trunk that breaks up into anterior 

 and posterior cerebral arteries, the first of which supplir.- 

 the cerebrum and olfactory bulbs, and the second, the rest 

 of the brain by branches to its dorsal and ventral surtiu -. 

 The latter unite upon the ventral surface of the medulla 

 oblongata, to form a median (myelonic) artery continued 

 backward along the spinal cord. 



Parker, Phil. Trans, vol. clxxvii. 1886, p. 690. 



D. 742. The brain of a Turtle (Chelone mydas) with the arterial 

 blood-vessels injected. The cut ends of the internal 

 carotids can be seen on either side of the infundilmlum. 

 Each divides on the base of the brain into two branch.-*, 

 one of which runs forwards and branches out over the 

 cerebrum and olfactory bulbs. The other passes backward* 

 and shortly unites with its fellow at the base of the 

 medulla to form the basilar artery, but gives oil' before this 

 union two large branches to the optic lobes and cerebellum. 



0.0. 1313 c. 



D. 743. The brain of a Goose (Anser /eras) with tho arteries 

 injected. Bristles have been inserted into the ruptured end 

 of the left olfactory bulb and into the roots of th- !" 

 cranial nerves. 



II nn'' 





