I 



SWEAT, EESPIRATORY AND VA SO-MOTOR CENTRES. 549 



epinal cord. It is clear, then, from these experiments, that the 

 respiratory centre is not confined to the medulla oblongata, but 

 extends to the spinal cord. Usually, however, the spinal part 

 of it is too weak to keep up the respiratory movements alono, 

 without the aid of the medullary part, and can only do so when 

 it is stimulated to excessive action by means of strychnia. This 

 conclusion is also borne out by the fact that when strychnia is 

 given to an animal before the division of the cord at tlie occiput, 

 the respiratory movements do not entirely cease at the moment 

 of division, as they usually do. And what is true of the respira- 

 tory centre holds also for the vaso-motor centre. When the 

 cord is divided at the occiput, the vessels being no longer under 

 the influence of the vaso-motor centre, usually dilate. But here 

 also, after the injection of the strychnia, the vaso-motor power 

 is restored, and the vessels again contract to a greater or less 

 extent. It is evident, then, that the vaso-motor centre, like 

 the respiratory, extends a certain distance down the cord, and 

 that it also, like the respiratory centre, is stimulated to increased 

 action by strychnia. 



Closely associated with these two centres appear to be the 

 sweat centres. It was first observed by Goltz that irritation of 

 the sciatic nerve would produce sweating in a limb, and it was 

 shown by Kendall and Luchsinger that this sweat was indepen- 

 dent of any alteration in the vascular supply, for it occurred in 

 animals poisoned with curare, where all the vessels going to the 

 limb had been tied ; and it even occurred in an anjputated leg 

 for a quarter of an hour after its severance from the body. The 

 nerve centres by which the sweat nerves are usually excited were 

 localised by Luchsinger in the spinal cord, but Nawrocki, who 

 repeated his experiments, came to the conclusion that the sweat 

 centre vras situated, not in the spinal cord, but in the medulla 

 oblongata, because he found that division of the spinal cord 

 high up arrested the secretion of sweat. The reason of this dis- 

 crepancy between the conclusions of Luchsinger and Nawrocki 

 probably is that the sweat centre, like the respiratory and vaso- 

 motor centres, is not confined either to the medulla or to the 

 cord, but extends through both. It is probable that, like the 

 respiratory and va^'O-motor centres, a great portion of the sweat 



