76 THE STRUCTURE OF THE FOWL 



inner stratum of muscle is composed of fibres 

 arranged mainly circularly. Separating the 

 two muscular strata is a layer of connective 

 tissue. In the thin - walled infundibulum 

 muscular tissue is scanty, and two definite 

 strata cannot be distinguished (Fig. 43). The 

 amount of muscle gradually increases until in 

 the uterus it is abundant, and forms a sphincter 

 where the uterus ends and the vagina begins. 

 In the vagina the outer stratum consists of 

 scattered bundles of fibres, but the inner 

 circular stratum is remarkably thick. (3) 

 Submucous connective tissue joins the muscular 

 tunic to the lining membrane. (4) The mucous 

 membrane constitutes the most important 

 part of the oviduct, since it is from the glands 

 therein that the albumen, shell - membrane, 

 and shell are derived. 



Examined with the naked eye the mucous 

 membrane is seen to be beset with longitudin- 

 ally and slightly spiral folds on the sides 

 of which are secondary folds. The folds are 

 highest in the albumen-secreting part of the 

 duct (Fig. 44) and least decidedly longitudinal 



of this organ." It seems possible that the muscle \\ithin the 

 ligaments — especially abundant at the caudal end of the ventral ^i 

 ligament — may assist in the movement of the egg along the duct. 



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