4O Practicum VI. The Parts of the Neck. 



and if not may be recognized from its tubular shape, more or less col- 

 lapsed. 



i. The vagus of the cat, in the neck, is contained in the same sheath 

 as the SYMPATHIC (sympathetic); in man the two are distinct. 



j. The two jugular veins, ectal and ental, may commonly be recog- 

 nized from containing some blood. 



15. The Trachea. Dissect off the muscles covering the ventral 

 aspect of the trachea ; cut off a piece of it, 1-2 cm. long and note that (a) 

 its cartilaginous rings alternate with softer tissue, and (t>) the ring are 

 not complete, the interval at the dorsal side being occupied by muscle and 

 fibrous tissue. 



16. The Larynx. Cephalad the trachea enlarges and is modified 

 to form the LARYNX, less prominent than in man where its projection is 

 called the "Adam's apple." Just cephalad of the larynx is a slender 

 bone, or rather chain of bony and cartilaginous segments, the HYOID 

 BONE, PI. I ; it is in the form of a U, its ends being attached to the base 

 of the skull just laterad of the hemispherical bony elevation, the TYM- 

 PANIC (or auditory) BULLA (PI. XVI). 



17. Removal of the Neck. Consult Plates I and XVI. Flex the 

 head and neck upon one another ; with the arthrotome divide the muscles 

 just caudad of the lambdoidal crest ; this will permit further flexion ; 

 continue to cut till there are reached two bony projections the OCCIPITAL 

 CONDYLES by which the skull articulates with the ATLAS (first vertebra). 



a. Work the parts on each other. Cut the capsule inclosing each 

 joint ; then the membrane at the meson, which will expose the NEURAXIS 

 at the junction of the myel with the brain. Divide it and pull away the 

 vertebrae and attached muscles from the ventral soft parts of the neck, 

 esophagus, trachea, etc. 



18. Removal of the Mandible (lower jaw). Unless the student has 

 done this before, the two halves (RAMI) should be removed separately. 



a. With the scalpel cut along the mesal (inner) side of the bone to 

 the SYMPHYSIS (mesal union between the tips of the rami). In young 

 animals the symphysis may be divided with the arthrotome or pocket 

 knife ; in older the coarse scissors or even nippers may be needed. In man 

 the rami are closely united at an early period. 



b. Work the ramus up and down and note that the attachment of the 

 ARTHRAL CONDYLE (PI. XVI) is inclosed by a FIBROUS CAPSULE. Push 

 a narrow, strong blade directly mesad for 10-15 mm. and continue to cut 

 cephalad and caudad till the bones are freed from one another. The 

 ramus may then be twisted and pulled away. Repeat with the ramus of 

 the other side. 



19. Pull the trachea and esophagus caudad and ventrad and dissect 

 them away from the base of the skull as far as the meatus. 



a. With the scissors slit the dorsum of the esophagus along the 

 meson. It expands cephalad as the PHARYNX (PI. XVII). 



b. Pull the trachea caudad. Pass a probe cephalad and note its 

 emergence into the pharynx through the GLOTTIS (the narrowed orifice of 

 the larynx ; also, cephalad of the orifice, the triangular, cartilaginous 

 i.i'ic.LOTTis, longer and more pointed than in man. 



20. Removal of the Larynx and Trachea. Note the U-shaped bone 

 at the side of the pharynx, the hyoid. Cut between it and the larynx, 

 and remove the latter with the trachea ($ is). Trim off the remnants of 

 the pharynx and esophagus. 



