44 Anatomy of the Nervous System 



The secondary visceral pathways are not well known. 

 They include descending fibres to the cervical spinal cord, 

 concerned probably with respiratory reflexes and reflexes of 

 the digestive organs, such as vomiting, and an ascending path 

 probably to the hypothalamus. Allen, however, has demon- 

 strated in the guinea pig that the ascending secondary fibres, 

 unless they are unmyelated, must run with the medial lem- 

 niscus of the opposite side to the thalamus. 



