nr 



below. In front it is closed by the bodies of the vertebrae ; but in 

 the skeleton its posterior part is imperfect, being filled up in the re- 

 cent state by membrane, and protected by the ligamentum nuchae. 



The author then describes the appearance, on dissection, of the 

 membranes of the spinal marrow, and of the mechanism by "which 

 its compression in the various and extensive motions of the neck is 

 prevented ; he also adverts to the exact correspondence between the 

 extent of motion permitted, and the size and form of the canal in 

 the human spine, and to some pathological consequences connected 

 with such structure. 



Drawings of some of the cervical vertebrae in birds, with a de- 

 scription of their different parts, are annexed to this paper. 



Of the Nerves which associate the Muscles of the Chest, in the ac- 

 tions of Breathing, Speaking, and Expression. Being a Continuation 

 of the Paper on the Structure and Functions of the Nerves. By 

 Charles Bell, Esq. Communicated by Sir Humphry Davy, Bart. 

 LL.D. P.R.S. Read May 2, 1822. [Phil. Trans. 1822, p. 284.] 



This paper forms the continuation of that printed in the last vo- 

 lume of the Society's Transactions, by the same author. In the 

 present communication the author proceeds to show that the office of 

 the respiratory apparatus is not confined to the changes produced 

 upon the blood, but that the same actions are employed in subservi- 

 ence to other organs, and that they perform a variety of functions, 

 as in the natural voice in articulate language, and in the expression 

 of passion, as well as in the more familiar acts of smelling, coughing, 

 sneezing, &c. 



Having established the proofs of the necessity .of a number of re- 

 mote parts being joined in the performance of these functions, he 

 proceeds to show that there is a distinct class of nerves for this pur- 

 pose. That these nerves depart from the same column of the spinal 

 marrow, and diverge to all the parts of the frame, which are drawn 

 into consent in the action of respiration. 



Proceeding to show the difference betwixt the calm and uniform 

 breathing for the purposes of circulation, and the excited and more 

 irregular actions, as in speaking, singing, coughing, and sneezing, he 

 proves the necessity of certain powerful muscles being brought in as 

 accessories and. aids to the common muscles of respiration. He nexts 

 shows that the respiratory nerves are entirely distributed to these 

 accessory muscles. 



After tracing these nerves, and disengaging them from their in- 

 tricate relation with the other nerves, he proceeds, by comparative 

 anatomy, and by experiments, to show that they are respiratory 

 nerves, and that their division cuts off the parts to which they are 

 respectively distributed from participating in the act of respiration. 



He takes occasion to show that authors have attended too ex- 

 clusively to the par vagum, or eighth pair of nerves, which is only the 

 principal or central nerve of an extensive class of nerves, which 



