Practicum VI. The Teeth. 39 



11. Transect the temporal and masseter on the other side in like 

 manner. Grasp the mandible and work it up and down ; then with the 

 forceps pull upon the cut end of the part of either muscle which is 

 attached to the mandible ; the movement of the latter illustrates the action 

 of the mujrcles by contraction. 



12. Functions of the Teeth. Work the mandible and note the rela- 

 tions of the mandibular and maxillary teeth. The MANDIBULAR CANINE 

 (PI. XVI, C] enters the DIASTEMA, the interval between the maxillary 

 canine and the incisors ; the other mandibular teeth pass mesad of the 

 maxillary ; the last (MOLAR) in the mandible (PL XVI, M) acts against 

 the last premolar of the maxilla like a scissors-blade ; hence these two 

 are called SECTORIAL TEETH. Their office is to cut the flesh ; the canines 

 hold and lacerate the prey, while the incisors are mainly used in gnaw- 

 ing bones. 



13. The Oral Cavity. Force the mouth open to its fullest width. 

 Draw out the tongue and look down the throat ; there should be visible 

 the free margin of the SOFT PALATE dorsad, and ventrad the triangular 

 point of the EPIGLOTTIS. Defer the examination of other features till 

 the mandible is removed. 



a. Looking into one's own mouth before a mirror the soft palate will 

 be seen to present a mesal appendage, the UVULA, which is absent in 

 the cat. 



14. The Arrangements of Parts in the Neck. See that the cut 

 caudal surface of the neck is as smooth as possible. Compare with Plates 

 XVI and XVII ; of course on the latter only the mesal parts are shown. 



a. The muscles are easily recognized ; their thickness in the dorso- 

 lateral region enables the cat to not only support its head in what would 

 be an impossible attitude for us, viz., with the neck erect while the body 

 rests on one side, but also to carry prey and its young. 



b. Make an outline diagram of the cut surface of the neck as follows : 

 Represent the outline of the whole by an approximately circular line, 

 twice the actual size. Indicate the MESON by a "meridian," a vertical or 

 dorso-ventral line at the middle of the circle ; parts of this line may be 

 erased when the drawing is finished. 



c. At the proper place on the meson, commonly near its middle, 

 represent the AXON, (body-axis) by a depressed circle ; if the transection 

 passed between two vertebrae the surface will be rather soft and smooth ; 

 if through the body or CENTRUM of a vertebra, then it will be hard and 

 rough. 



d. Dorsad of the axon is a subcircular space, the NEURAL (spinal) 

 CAVITY ; the general outlines of the bony arch may be indicated. 



e. The NEURAXIS is represented by the nearly cylindrical MYEL or 

 spinal cord ; the exact form and the details of its structure will be studied 

 later. 



f. Near the ventral side, covered by thin muscles, is the TRACHEA 

 or wind-pipe ; the cartilaginous rings of which it partly consists cause it 

 to maintain its form. It is approximately circular, but since the dorsal 

 side of each ring is membranous that side is slightly flattened. 



g. But the walls of the ESOPHAGUS, just dorsad of the trachea, are 

 composed of muscle and mucosa, and therefore collapse ; on the drawing 

 it should be represented as a flattened or corrugated circle. 



h. Laterad of the interval between the trachea and esophagus at 

 either side are two very important structures, the CAROTID ARTERY and 

 the VAGUS (pneumogastric) NERVE. The artery may contain some blood 



