MOTOR FUNCTIONS OF THORACICO-L UMBAR O UTFLO IV 35 



the vagus is the motor nerve to the muscles in the spleen. That 

 this is not so has been shown by Schafer and Moore, who have 

 given evidence for the origin of the motor fibres to the spleen 

 from the thoracic region. They point out that Bulgak came to 

 the conclusion that the fibres cohcerned with the innervation of the 

 spleen pass to their distribution by way of the anterior roots from 

 the third thoracic to the tenth thoracic and the greater splanch- 

 nic nerves of the left side only, thence through the semilunar 

 ganglion by the nerves accompanying the branches of the splenic 

 artery. They themselves find that the anterior roots concerned ex- 

 tend from the third thoracic to the end of the thoracico-lumbar out- 

 flow, and exist on both sides of the body, but the effect is more 

 marked on the left side. By the use of nicotine intravenously in- 

 jected they show that the splenic nerves continue to act, when 

 stimulation of the cord produces no effect and stimulation of the 

 splanchnic nerves produces only the very slightest appreciable 

 contraction. The motor nerves to the splenic muscles therefore, 

 like all other motor nerves to involuntary muscles, are not affected 

 by nicotine ; consequently, if they existed in the splanchnics, they 

 should show their action when the splanchnic is stimulated after 

 a full dose of nicotine ; the hardly appreciable contraction which 

 occurs may mean that a few motor nerves to the spleen exist 

 in the splanchnic nerves, arising from some of the nerve cells of 

 the lateral sympathetic chain, or that the contraction is due to 

 adrenalin thrown out from chromaffine cells by the stimulation of 

 the splanchnics (see p. 141). The conclusion is that the motor 

 neurons for the splenic muscles are situated in the semi-lunar 

 ganglion. 



There is absolutely no evidence of any vaso-constrictor nerves 

 in any of the other cranial nerves or in connexion with the sacral 

 outflow. In all cases, wherever the blood vessels may be, their 

 motor innervation comes from cells connected with the thoracico- 

 lumbar outflow of connector fibres. 



The systematic investigation of the anterior roots of this re- 

 gion by various observers, especially by Bradford and by Langley, 

 enables us to draw up the following table, showing the motor 

 nerves to the blood vessels in an animal with seven lumbar 

 vertebrae. 



