DIGESTION i 59 



and 764 c.c. respectively. Since division of the nerves both pre- and post- 

 ganglionic, does not diminish or abolish the secretion, the inference is that 

 the pilocarpin exerts a stimulating action on the nerve endings in connection 

 with the gland cells. This inference is strengthened by the fact that the 

 pilocarpin effect is antagonized and the secretion checked by a suitable dose 

 of atropin, the seat of the action of which is known. The two alkaloids thus 

 appear to be in physiologic antagonism in their action on these nerve termi- 

 nations. The action of pilocarpin is not limited to the salivary glands, but 

 extends to glands found in the alimentary canal, respiratory passages, and 

 skin. 



DEGLUTITION 



Deglutition is that part of the digestive process which is concerned in 

 the transference of the food from the mouth through the pharynx and 

 esophagus into the stomach. This is an extremely complex act and involves 

 the action of a large number of structures, all of which are made to act in 

 proper sequence under the coordinating influence of the nerve system. The 

 deglutitory canal consists of the mouth, pharynx, and esophagus, each of 

 which presents certain anatomic features on which its physiologic action 

 depends. 



The Mouth. The cavity of the mouth is bounded in front and on the 

 sides by the alveolar arches and the teeth; the roof is formed by the hard 

 palate and the floor by the tongue. Anteriorily, the mouth communicates 

 with the exterior by a transverse opening the buccal orifice, and posteriorly 

 with the pharynx by an opening, the isthmus of the fauces. The cavity of 

 the mouth is lined by mucous membrane in which are imbedded numerous 

 mucous glands. The interior of the mouth is separated in part from the 

 .interior of the pharynx by an incomplete septum formed above by the soft 

 palate, laterally by the anterior and posterior palatal arches and below by 

 the tongue. 



The Pharynx. The pharynx is an oval-shaped cavity extending from 

 the base of the skull to the lower border of the cricoid cartilage, a distance 

 of about 12 centimeters. Its walls are formed mainly by three pairs of 

 muscles the superior, middle, and inferior constrictors each consisting 

 |of red, striated muscle-fibers, and hence capable of rapid and energetic con- 

 tractions. Superiorly the pharynx is attached to and supported by the 

 basilar process of the occipital bone; inferiorly it becomes continuous with 

 the esophagus. The anterior wall of the pharynx is imperfect and presents 

 openings which communicate with the nasal chambers, the mouth, and the 

 ilarynx. The lateral wall on either side presents the opening of the Eustachian 

 tube which leads directly into the cavity of the middle ear. The interior of 

 the pharynx is lined by mucous membrane. The pharynx is partially sepa- 

 rated from the mouth by the velum pendulum palati, a muscular structure 

 attached above to the hard palate; its lower edge or border^ is directed 

 idownward and backward and presents in the middle line a conical process, 

 the uvula. On either side the palate presents two curved arches, the anterior 

 and posterior, formed respectively by the palato-glossei and palato-pharyngei 

 muscles. The superior laryngeal aperture is placed just beneath the base 

 of the tongue. It is triangular in shape, wide in front, narrow behind, and 

 directed downward and backward. It is bounded above by a thin plate of 



