鶏の消化に関する基礎的研究Ⅰ : 食塊の嚥下部位および筋胃運動について

　成鶏10羽について，無砂粒飼料を給与して消化管内から砂礫を完全に消失せしめた後，硫酸バリウムを混じた4種類の試験飼料・チュウインガム球およびガラス球・砂礫等を摂食せしめ， X線透視および間接撮影法により食塊の嚥下部位を検討するとともに筋胃嚢を造影し，また筋胃に銀線を縫い付けた後，X線観察によって筋肉運動を研究した.その結果は次の通りである.
1) 給与形態の異なる試験飼料の嚥下食塊は，摂食当初は嗉嚢に入ることなく直接筋肉へ到達したが，爾後の食塊は嗉嚢内へ嚥下して滞留する.
　直接筋胃に入る食塊量は数gと推定された.
2) 試験飼料は粒餌，粉餌の別なしまた粒餌では粒の大小に関係なく，食塊は同一径路により嚥下される.また鶏が空腹，満腹の何れの条件下でも，食塊の礁下部位には差違がない.
3) 軟質のチューインガム球は嗉嚢内へ，ガラス球・砂礫では筋胃内へ殆と・全て嚥下した.
4) ガラス球・砂礫を飽食せしめても，嗉嚢内へ嚥下して滞留することは殆どない.
　　砂礫の摂取は筋胃機能に必要とする量に留まると判断される.
5) 運動休止期の筋胃嚢は腹腔中央部より前側に位置し，円柱状を呈し，前方に傾斜して存在する.
6) 筋胃連動の開始とともに胃嚢は次第に後方へ傾き，遂には休止期の位置に対して反転した形態の後球型となり，直ちに弛緩して休止期に移る運動を反復する.
7) 連動開始から胃嚢反転に至る運動は，比較的緩慢な速度で進行し，収縮は顕著でなく，胃嚢位置の移動を伴う運動を主とし，その直後に起る胃嚢球型収縮は短時間に経過する強烈な収縮弛緩運動である.
8) 筋胃外側に縫着した銀線の位置は，収縮運動中に胃嚢形態に著変があったにも拘わらず変化が殆ど認められない.
　筋胃嚢の運動は蠕動的でなく， むしろ反芻獣の第2胃運動に類似した強力な収縮運動であると判定された.
9) 筋胃における食糜の機械的作用は，特に胃嚢球型収縮期に行なわれるものと判定され， また食塊の筋胃への進入は休止期の直前，十二指腸への移行は球形収縮期に行なわれることが示唆された.

These experiments were conducted with 10 hens raised on a gritless ration. After the disappearance of grit from the digestive tract (Fig. 2), 4 kinds of experimental food (5-10, 10-20, 20-30 mesh size grain, mash) and chewing-gum ball (3-7mm in diameter) containing BaSO., glass ball (3-8mm in diameter) and grit (10-20 mesh size) were given to them for the investigation of the place of deposition of the bolus as well as the movements of the gizzard by X-ray observations. And the movements was also observed from the changes of position of the silver wire attached to the outside of the gizzard (Fig. 1).

The results are as follows :
1) On feeding different types of food, the first boluses were swallowed directly into the gizzard, but the remainder lodged in the crop (Text-fig. 1). The directly swallowed amounts into the gizzard seemed to be few grams.
2) The place of deposition of the bolus was the same in any case of grain or mash feeding. And also the place was the same in any state of being hungry or full-fed (Figs. 3, 4, 5, 6).
3) Chewing-gum ball entered the crop (Fig. 7), glass ball and grit passed directly across the dorsal portion of the crop into the gizzard (Figs. 8, 9).
4) Almost all of the glass ball and grit never lodge into the crop even if in the full-fed state. The amount of grit intake is deemed just as much as necessary for the gizzard functions.
5) The gizzard sac at the relaxation pause present a cylinder shape inclining forward in the center of the abdominal cavity (Figs. 11, 12).
6) The gizzard sac was observed to present three waves (Text-fig. 2), namely two kinds of contractions and one relaxation. Firstly, the sac gradually began to incline backward and finally formed a reverse shape to the resting state (Figs. 14-16, 20-21). Secondly, it presented a round shape (Figs. 17,22), which occured rapidly and powerfully, and then followed the relaxation of resting pause (Figs. 18, 23). Mean cycle of movement occured at intervals of 20 sec.
7) The contraction of forming a reverse shape took longer interval than that of a round shape. The former occupied 8-10 sec. and the latter, 2-3 sec.
8) The silver wire attached to the outside of gizzard was not obviously influenced by the change in the shape and position of the gizzard throughout the contractions (Figs. 19-23). These facts suggest that the pattern of motility of the gizzard sac would not be peristaltic like the intestine, but they would be powerful contractions similar to those of the reticulum of ruminants.
9) It is very probable that the grinding action of the bolus in the gizzard would be carried out mainly at the stage of the round-shape contraction. And it is also suggested that the boluses would enter the gizzard just before the relaxation and pass into the duodenum at the round-shape contraction.