-SPLANCHNOLOGY 143 



The submucosa connects the mucous membrane to the muscular 

 coat. 



The wall of the crop is provided with strong muscles. The 

 fibrous coat, or tunic, connects it with the surrounding structures^ 



.Function. — The crop is a storehouse for the food during the hours 

 of feeding, the food when needed by the. stomach being gradually 

 discharged from the crop by the contraction of its muscular walls. 

 The subcutaneous cervical muscles which cover this reservoir aid in 

 this discharge. 



In the act of deglutition, the food, after being subjected to the 

 fluid supplied in the mouth by the adjacent glands, is poised upon 

 the tongue and swaUowed partly by a sudden jerk of the head, and 

 partly by means of the pressure of the tongue against the hard 

 palate, the food then passes down the esophagus and lodges first 

 in the crop, till needed by the stomach, when it is' passed through the 

 second portion of the esophagus to the first portion of the stomach, 

 the proventriculus. The time during which food remains in the 

 crop depends upon the nature of the food. Animal food will, iri) 

 part, be retained about eight hours and vegetable foods may not alr^ 

 be passed on for from sixt-een to eighteen hours. ■^ 



The Stomach (Fig. 31, No. 7; Fig. 32, B). — The stomach, or 

 ventriculus, of fowls is made up of two portions, namely, the pars 

 glandularis, or proventriculus, and the pars muscularis, or gizzard. 



The Proventriculus. Location.— Tht proventriculus lies in the 

 superior part of the groove formed by the two lobes of the hver, is 

 inferior to the aorta, and is directed slightly to the left, communicat- 

 ing anteriorly with the second portion of the esophagus and poste- 

 riorly emptying into the pars muscularis, the gizzard. 



Shape. — The proventriculus is round transversely and elongated, 

 in fact, nearly fusiform. In the hen of average size it measures about 

 1.62 inches long and 0.8 inch in diameter. 



Structure. — The wall of the proventriculus has four coats, the 

 mucous, submucous, muscular, and serous. 



The inner mucous coat which is raised in folds, is lined with 

 columnar epithelial cells. The mucous membrane contains lymph- 

 oid tissue. The mucous coat throughout contains simple tubular' 

 glands which secrete a highly acid fluid which finds its way to the 

 surface through small cylindrical ducts lying at right angles to the 

 inner surface of the mucous membrane (Fig. 32, No. .B, i). 



