38 DB. J. MTJEIE ON THE MANATEE. 



nerves of man and some of the higher mammalia, it would seem that the two first- 

 mentioned of these three nerve-divisions in the main corresponds with the distribution 

 of the fourth cervical nerve, while the third division rather appertains to the fifth. 



V. The fifth nerve is thicker at its origin than is the fourth nerve. It leaves the 

 spinal canal through the foramen between the third and fourth cervical vertebrae pre- 

 sent ; and while one portion of it joins the fourth nerve where the phrenic is given 

 off as aforesaid, the other, its main trunk, is sent down and outwards to join the sixth 

 nerve, at the same time about its middle transmitting a branch deeply to the subsca- 

 pularis muscle. 



VI. The sixth cervical nerve has a still thicker trunk than the last (5th), and it 

 comes out from the foramen between the fourth and fifth cervical vertebrae. Its first 

 offshoot, a cord of considerable calibre, is that uniting it with the fifth, and which 

 runs outwards towards the subscapularis muscle near the shoulder-joint ; thence it passes 

 round the head of the humerus, and ultimately becomes the circumflex nerve of the 

 fore limb. 



Other nerve-branches supply the subscapularis, the teres, and rhomboid muscles ; and 

 still another passes apparently to the latissimus dorsi or neighbouring muscles. Pre- 

 vious to where these separate, there is a union with the cord forming the musculo- 

 spiral. What appears as a main trunk of the sixth, or after its junction with the fifth, 

 proceeds towards the seventh, and forms with it a broad nervous expansion at the root 

 of the median. From this expansion fibres either of the sixth or the seventh branch 

 off to the biceps humeri. Another nerve, either derived as a continuation of the sixth 

 or, it may be, seventh cervical, supplies the pectoral muscles. From the same point two 

 other nerves strike off divergingly — one, namely, joining on to the branch of the eighth 

 supplying the thoracic region, and the other forming a communication with the upper 

 part of the ulnar. 



VII. The seventh cervical trunk emerges between the fifth and sixth vertebrae. As 

 a thick cord it first sends a union to the eighth nerve ; then its main continuation goes 

 onwards, becoming the median nerve of the arm ; but at the commencement of this 

 (that is, from the nervous expansion above spoken of as derivative from the sixth) a nerve 

 is sent to the larger belly of the biceps muscle. In close proximity to its junction with 

 the trunk of the eighth nerve a cord is derived which passes over the insertion of the 

 latissimus dorsi, sends a long filament to that muscle, and, winding round the neck of 

 the humerus, becomes the musculo-spiral nerve of the arm. Its (the seventh's) con- 

 nexion with the sixth cervical nerve has already been mentioned. 



Vni. The eighth cervical nerve comes out above the first rib. Its great thick trunk 

 sends a branch which unites with the first intercostal nerve, and gives twigs of supply to 

 the scalenus muscle and to the vascid.ar plexus around and just within the chest-cavity. 

 The main cord immediately thereafter receives an accession of fibre from the bridge of 

 union with the seventh nerve aforementioned, and just beyond expands or takes the 



