596 



oxygen of the atmosphere on the spinal cord, the paralysis of the 

 blood-vessels of this organ, and the state of rest of the muscles and 

 motor nerves of the limb. 



If we compare the side of the face where the sympathetic has 

 not been divided, with the posterior limb on the uninjured side of 

 the spinal cord, we find that they also have a great many points of 

 resemblance. They both receive less blood than usual, their tem- 

 perature diminishes, their nutrition is less active, and their vital 

 properties also diminish. 



IV. " Experimental Researches on the Influence of Efforts of 

 Inspiration on the Movements of the Heart." By E. 

 BROWN-SfcQUARD, M.D. Communicated by JAMES 

 PAGET, Esq., F.B.S. Received June 25, 1857. 



A very interesting fact, of which many circumstances have been 

 carefully investigated by Professor Bonders and Dr. S. W. Mitchell, 

 has received a wrong explanation from those physiologists. This 

 fact consists in a diminution of either the strength or the frequency 

 of the beatings of the heart, when an energetic effort at breathing 

 is made and maintained for half a minute or a little more. Pro- 

 fessor Bonders thinks that this influence of inspiration on the 

 heart is due to a mechanical agency of the dilated lungs on this 

 organ. 



They admit that the state of the lungs has a great influence on 

 the heart, but the principal cause of the diminution in the move- 

 ments of this organ is very different from what has been supposed 

 by Professor Bonders, by Professor J. Mueller, and others. It is 

 known that when the medulla oblongata, or the par vagum are ex- 

 cited (either by galvanism, as the Brothers Weber have discovered, 

 or by other means, such as a mere compression, or a sudden wound, 

 as I have found), the heart's beatings diminish or cease entirely. 

 Whether this stoppage be due to the cause I have attributed it to 

 or not, is indifferent to my present object. What is important 

 is, that in these cases an irritation on the origin of the par vagum 

 acts through it on the heart to diminish or to destroy its action. 



