350 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



the saw only for the bony parts. After having sawed through the roof of the 

 skull, cut down through the brain with a single sliding stroke of a blunt knife 

 like a table knife. The brain and skull should thus be cut in two, one part 

 being slightly larger than the other. Wash the cut surfaces gently under the tap, 

 and study the nasal cavities. 



The nasal cavities are very long in the rabbit, shorter in the cat. They are 

 divided into right and left cavities or fossae by a perpendicular plate, the septum 

 of the nose, which is present on the larger section of the head. The septum 

 consists of cartilage anteriorly and of thin bone posteriorly, the latter being the 

 perpendicular plate of the ethmoid bone. On the smaller section the lateral and 

 posterior walls of the nasal fossa are seen to be occupied by delicate scrolled and 

 folded bones, the turbinated bones or conchae. In the rabbit these are readily 

 divisable into an anterior concha, the inferior concha or maxilloturbinal, much 

 folded and located on a separate small bone of the skull; a middle concha or 

 nasoturbinal, a long single fold dorsal to the preceding and dependent from the 

 nasal bone; and the superior concha or ethmoturbinal, part of the ethmoid bone. 

 In the cat the turbinals are closely crowded together, but by prying them apart 

 gently there can be distinguished a small anterior maxilloturbinal on the maxilla ; 

 above this a single fold, the nasoturbinal, dependent from the nasal bone; and a 

 great mass of folds, the ethmoturbinal, filling the greater part of the nasal fossa. 

 The ethmoturbinals are also called the ethmoid labyrinths, and the spaces inclosed 

 by the bony folds are called the ethmoid cells. Definite passages known as the 

 meatuses of the nose run between the conchae and conduct the air to the naso- 

 pharynx. They connect with the nasopharynx below the ethmoturbinals. 



The posterior dorsal part of the nasal fossa is closed by the cribriform plate 

 of the ethmoid which unites with the perpendicular plate of the ethmoid bone 

 medially and with the parts of the ethmoid which bear the layrinths laterally. 

 The anterior end of the brain (olfactory bulbs) is readily seen to abut against 

 the cribriform plate, and through this plate the fibers of the olfactory nerve pass 

 from the olfactory membrane covering the ethmoid labyrinths to the olfactory 

 bulbs. 



c) The structure of the ear: Carefully remove the brain from the two halves 

 of the skull, preserving the latter. In doing this the roof of the skull may be 

 cut away. Loosen the brain on all sides by passing a blunt instrument between 

 the brain and the skull. The tough membrane, the dura mater, which covers 

 the brain should be retained with the brain. Carefully cut the cranial nerves 

 where they pass through the foramina of the skull, leaving their roots attached 

 to the brain. Note the small round reddish body, the pituitary body, attached to 

 the ventral surface of the brain, set into a depression in the floor of the skull; 

 keep this body attached to the brain if possible. Preserve the two halves of the 

 brain in a vessel of water or, if they are to be kept for some time, in weak formal- 

 dehyde. 



