On the Influence of Efforts of Inspiration on the Heart. 543 



relation to the theorem referred to at the coiiclusion of the former 

 memoir, and an apphcation to the determination of the expression 

 for P (1, 2, 3, 4, 5, 6) 5-. 



" On the Anatomy and Physiology of the Spongiada." By J. S. 

 Bowerbank, F.R.S., F.L.S. &c. 



" On the Fructification of certain Sphaeriaceous Fungi." By Fre- 

 derick Currey, Esq. 



"On the Anatomy of Tridacna." By John Denis Macdonald, 

 Esq., Assistant-Surgeon, R.N. 



"Experimental Researches on the Influence of Efforts of Inspira- 

 tion on the Movements of the Heart." By E. Brown-Sequard, M.D. 



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. Ihis 

 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 Donders 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 Donders, by'Professors J. Miiller, 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. 

 I thought that it would be interesting to decide, if, at the 

 time that there is an effort at inspiration, there is not also an influ- 

 ence of the medulla oblongata on the par vagum, more or less 

 similar to that which exists when we galvanize or otherwise irntate 

 the medulla oblongata. To ascertain if it is so, I have made ex- 

 periments on newly-born animals, and on birds. As I have already 

 published some of the results of my researches on newly-born animals, 

 and as these results are not so completely decisive as those of my 

 experiments made on birds, I will merely give here a summary of 

 what I have seen in these last animals. I have found the same 

 facts in ducks, geese and pigeons; but as I have repeated the 

 experiments more frequently on the last-mentioned animals, I will 

 speak of them only. When their abdomen has been widely opened 

 and their heart exposed to sight, pigeons may live, as it is well 

 known, for a long while. I wait until they are almost dying, having 

 only one, two, or three inspirations in a minute, and then, if the 

 weather is cold, and if the animal has lost many degrees of its 



