Lull — Functions of the " Sacral Brain " in Dinosaurs, 475 



Birds. — The vagus (X) of birds arises behind the glos- 

 sopharyngeal (IX) and is connected therewith as well as 

 with the sympathetic system. After receiving branches 

 from the hypoglossal (XII) and taking up the spinal 

 accessory (XI), the vagus runs down the side of the 

 oesophagus to the ventral side of the proventriculus, 

 where, joining its fellow from the other side, it spreads 

 out to supply the stomach. Other branches, leaving the 

 principal stem of each vagus, supply the liver, heart, and 

 lungs, and, as the recurrent laryngeal branch, also supply 

 the distal portions of the trachea and oesophagus. Some 

 fibres of the vagus often extend beyond the stomach, and 

 are connected with the sympathetic nerves of the trunk, 

 supplying parts of the intestinal canal. (Newton.) 



The approximate agreement in the innervation of both 

 birds and crocodiles is further argument for dinosaurian 

 innervation. 



Certain of the spinal nerves (dorso-lumbar) communi- 

 cate with the sympathetic system and thence with the 

 alimentary canal, but their function, in so far as it has 

 been observed, principally in man and certain mammals, 

 is inhibitory, and hence the reverse of a stimulus to 

 digestion. Such sacral nerves as do pass to the alimen- 

 tary canal are distributed to the hinder portion only, 

 beyond the glandular or digestive part. They are stimu- 

 lating, not inhibitory nerves, but their function is merely 

 the elimination of faecal matter and is in no other sense 

 digestive. 



The stomach in the mammal at least is largely auto- 

 matic in its movements, as is the heart, and while its 

 activity may be initiated or inhibited by impulses from 

 the vagus or sympathetic nerves, the stimuli which cause 

 the rhythmic movement originate in the muscles them- 

 selves, for this movement will continue after the sever- 

 ance of all nerve connection with the cerebro-spinal or 

 sympathetic centers. The reptilian heart is notorious 

 for its automatic contraction after its excision from the 

 body, and in all probability the heart and stomach of a 

 dinosaur were fully as automatic. 



All of this seems to show that we have no right in 

 assuming for the dinosaur an innervation or functioning 

 of the alimentary canal at variance with the standardized 

 type of the living amniotic vertebrates. 



