2 TOPOGRAPHICAL ANATOMY OF THE 



M. serratus dorsalis caudalis. — The fibres of the caudal portion 

 of the dorsal serratus are arranged in an oblique cranial and ventral 

 direction. They terminate in very definite slips or digitations that are 

 inserted into the caudal border of the last eight or nine ribs. 



M. serratus dorsalis cranialis. — The fibres of the cranial muscle 

 run obliquely in a ventral and caudal direction, and end in digitations 

 that are attached to the cranial border of the ribs, from the fifth or 



M. 



M. trapezius thoracalis. 

 M. latissimus dorsi. ' 

 Dorsal cutaneous nerves (thoracic). | 



M. obliquus externus abdominis. 

 Dorsal cutaneous nerves 

 (lumbar). , 



N. iliohypogastricus. , i i 



N. ilioinguinalis. ] | [ 



triceps brachii. 

 M. deltoideus. 



Lateral cutaneous nerves. 



M. pectoralis profundus. 



Fig. 1. — Superficial dissection of the Thorax and Abdomen before 

 removal of the Limb. 



sixth to the eleventh or twelfth, 

 covered by the caudal muscle. 



Two or three of these digitations are 



Dissection. — Iveflect both serratus muscles bv making a longitudinal 

 incision through their aponeurotic tendon of origin. In reflecting these 

 muscles it will be found that the hmibo-dorsal fascia detaches a partition 

 that passes inwards between the adjacent borders of the longissimus 

 dorsi and ilio-costalis muscles. This will require to be cut through 

 before the ilio-costalis can be thoroughly exposed. 



'i'he reflection of the dorsal serratus reveals three deeper muscles. 

 The largest and longest of these is the longissimus dorsi. It is the 

 chief occupant of the groove foi'med by the ribs and the spinous 

 processes of the vertebrae. The narrow lateral muscle, m. ilio-costalis, 

 is readily distinguished by its numerous tendinous attachments to the 

 ribs. The third muscle is the shortest and lies medial to the longissimus, 

 with which it is continuous, where the thoracic spinous processes are 

 longest. 



The dissector will observe a series of cutaneous nerves piercing the 



