DISSECTION OF THE NERVOUS SYSTEM. 375 



dorsal (posterior) root of the 6th left cervical nerve ; ganglia are present on all as shown in 

 this figure ; see also Fig. 109. Hemisphaerae Cerebral hemispheres, prosencephalon ; 

 see Chap. X. MM. (Iv. scp.) levator anguli scapulas et serratus (magnus) ( 664). M. 

 sbscp., M. subscapularis The light streak between this and the preceding muscle is 

 the glenoid border of the scapula (Fig. 44). M. supraspinatus See 673. MM. tra- 

 pezii Trapezius muscles ; see Fig. 66. N. accessorius The spinal accessory nerves (xi) ; 

 this nerve passes along the ental surface of the trapezius muscle ; see also Chap. X. N. 

 crcm., N. circumflexus ( 1024). N. ctn. int., N. cutaneus internus ( 1021). N. 

 hpgls., N. hypoglossus The 12th pair of cranial nervea ; Chap. X. N. latis., N. latis- 

 simus Nerve of the M. latisaimiis dorsi ( 1023). N. medius s. medianus ( 1025). N. 

 m. spiralis, N. musculo-spiralis ( 1026). N. m. ctn., N. musculo-cutaneus ( 1022). 

 NN. myen., dv. dsl., NN. myelencephalici, divisio dorsalis (15) Dorsal (posterior) 

 primary division of the first 15 myelencephalic or cerebro-spinal nerves. NN. myen., dv. 

 vnt. (15), NN. myelencephalici, divisio ventralis The ventral (anterior) primary divi- 

 sion of the first 15 myelencephalic or cerebro-spinal nerves. N. oc. (occipitalis) major 

 This forms the dorsal part of the 2d cervical nerve ; it receives a large anastomotic branch 

 from the 3d cervical nerve ; this nerve is distributed to the dorsal and caudal regions of 

 the head ; in the 1st and 2d cervical nerves the dorsal primary divisions are as large or 

 larger than the ventral ( 1007). N. rhmb., N. m. rhomboidei Nerves of the romboideus 

 muscle. N. sbscp., N. subscapularis ( 942 and 1023). N. spscp., N. suprascapu- 

 laris A large nerve from the brachial plexus ; it sends a branch to the clavicular end of 

 the clavo-trapezius, but is mainly distributed to the scapular muscles ; it is in company 

 with the suprascapular artery ; see 937, 1020, and Fig. 105. N. suboccipitalis The 

 1st myelonal nerve ; its name is not written, but it traverses the Fm. atl. with the A. ver- 

 tebralis. N. thr. post., N. thoracicus posterior The external respiratory of Bell ( 1029); 

 see 1019 for the internal respiratory or phrenicus. N. ulnaris ( 1028). 



1008. General Directions for Dissecting the Nervous Sys- 

 tem. The precautions mentioned in 596 (10) should be carefully 

 observed, and especial care taken that the part under examination 

 should be in a good light. Employ a tripod magnifier (Fig. 36) 

 whenever necessary to determine the course or relations of small 

 branches. Change the position of the cat as often as is necessary 

 to get the given part in the best light or to make it more accessible. 



Whenever a part is dissected, it should be kept moist by recov- 

 ering it with skin or sheet rubber, or by placing upon it a tuft of 

 cotton wet with 15 per cent, glycerin ( 170). 



In fresh animals, nerves may be distinguished from connective 

 tissue or empty vessels by their glistening and wavy or crimped 

 appearance when looked at closely. An uniujected vessel may 

 always be distinguished by cutting a slit in it and demonstrating 

 its tubular character with the tracer. 



1009. Instruments and Material Fifteen per cent, glycerin ; cotton ; towels or 

 cloths ; pins ; tracer ; fine, coarse and bone scissors ; nippers ; scalpels ; arthrotome ; 

 injecting apparatus and material (Chapter IV) ; skeleton, and a natural skeleton of the 

 arm ( 252). 



