HEAD AND NECK OF THE HORSE 17 



Dissection. — The trapezius muscle should be reflected after an incision 

 has been made througli it close to its origin from the ligamentum nuchse. 



N. ACGESSORIUS. — At a later stage in the dissection it will be found 

 that the accessory or eleventh cerebral nerve divides into two branches 

 ventral to the wing- of the atlas. The ramus ventralis has already 

 been seen to enter the sterno-cephalic muscle not far from its tendon 

 of insertion. The ramus dorsalis, now being investigated, receives 

 branches from the second and third cervical nerves in its course along 

 the neck under cover of the brachio-cephalic muscle. It reaches the 

 dorsal border of this muscle and travels along it for a short distance. 

 Covered by the cervical part of the trapezius, the ramus pursues a wavy 

 course over the ventral serrate (cervical part), deep pectoral (prescapular 

 part) and supraspinous muscles, to end in the thoracic part of the 

 trapezius. 



M. RHOMBOIDEUS CERVICALIS. — The rounded cervical rhomboid ^ 

 muscle arises, by short bundles of tendinous fibres, from the ligamentum 

 nuchas from the level of the second cervical to the second thoracic 

 vertebra. It has a thin, nan'ow, pointed extremity opposite the epi- 

 stropheus and increases in volume as its insertion to the medial surface 

 of the scapular cartilage is approached. 



M. BRACHiocEPHALicus. — It is generally accepted that the sterno- 

 cleido-mastoid muscle of man is represented in the horse by two 

 distinct muscles — the sterno-cephalic, already examined, and the 

 brachio-cepbalic. 



Owing to degeneration of the clavicle, the clavicular part of the 

 deltoid muscle of the human body is moreover represented in that part 

 of the horse's brachio-cephalic^ that extends from the level of the 

 shoulder joint to the humeral attachment of the muscle. In this 

 connection it should be noted that it is generally possible to find the 

 trace of a transverse tendinous intersection, representing the clavicle, 

 in the brachio-cephalic muscle opposite the shoulder joint. 



The fact that the accessory nerve supplies the sterno-cephalic and a 

 part of the brachio-cephalic, and that the axillary nerve supplies the 

 humeral end of the brachio-cephalic, lends support to the view stated 

 above. 



The brachio-cephalic muscle has attachments to the ridge forming 

 the lateral boundary of the groove on the humerus, the fascia of the 

 arm, the transverse processes of the second, third and fourth cervical 



^ Rhombus [L.], pd/x^os (rhombos) [Gr.], a rhomb. elSos (eidos) [Gr.], form. 

 2 Brachium [L.], ^pax^ojv (brachion) [Gr.], the arm above the elbow. Ce2)halicus 

 [L.], K€(pa\LK6s (cephalicos) [Gr.], pertaining to the head {K€<pa\ri). 

 2 



