200 PHYSIOLOGY CHAP. 



Other fibres traverse the anterior column of the spinal cord, and 

 leave by the anterior roots of the tract that extends from the 5th- 

 10th dorsal vertebrae ; they then unite with the splanchnics and 

 to a less extent with the sympathetic chain. 



In the olives of the bulb there is, according to Openchowski, 

 an inhibitory centre that determines the opening of the pylorus 

 by fibres which descend in the cord, and unite after leaving it 

 with the sympathetic. 



In the upper part of the cord, again, there are centres, which 

 on excitation cause the cardia to open. The efferent fibres descend 

 in the anterior cord, and then leave the anterior roots, and unite 

 with the dorsal sympathetic chain, with the aortic plexus, and the 

 small splanchnic. 



Although the afferent paths, which by acting on these centres 

 may reflexly determine the movements of the stomach, have not 

 been fully worked out, it is proved by Openchowski's work that 

 excitation of the kidneys, uterus, bladder, loops of the intestine, 

 and sciatic of animals in which all the nerve paths and centres are 

 intact may induce opening of the cardia. This fact accounts 

 for reflex vomiting, which not seldom accompanies diseases of these 

 parts, like that which is easily induced in man merely by slight 

 mechanical stimulation of the roots of the tongue, the pharynx, 

 and the palate. 



An important contribution to our knowledge of the significance 

 which must be attributed to the afferent paths, and, generally 

 speaking, to the peripheral stimuli, in the production and normal 

 course of vomiting has recently been made by A. Valenti (1906). 

 Experimenting with dogs and cats, he found that if a well-defined 

 zone of the pharyngeal mucous membrane was anaesthetised with 

 cocaine, between the lower part of the buccal cavity and the 

 higher part of the oesophagus, the animal lost the capacity of 

 expelling substances from the stomach, although on the action of 

 emetics (apomorphine, tartar emetic, copper sulphate) all the other 

 phenomena of vomiting were exhibited. This incapacity is due to 

 the fact that under such experimental conditions the active opening 

 of the cardiac sphincter does not come off. This opening is, how- 

 ever, a reflex act, due to excitation of the said zone of the pharyngeal 

 wall. According to Valenti this reflex has no connection with the 

 reflex of deglutition, the peripheral area of which lies, as we have 

 seen, in a more anterior region of the soft palate. In normal 

 vomiting this region of the mucous membrane is stimulated, 

 according to Valenti, by waves of peristaltic contraction from the 

 oesophageal walls, or more probably, perhaps, by the passage of 

 the saliva, which is regularly swallowed prior to vomiting. 



Valenti's work accounts clearly for the mechanism of reflex 

 vomiting on tickling of the fauces, since it is evident, as we have 

 seen, that pharyngeal- oesophageal anaesthesia is capable of pre- 





