. The physiology of domestic animals ... Physiology, Comparative; Veterinary physiology. 380 PHYSIOLOGY OF THE DOMESTIC ANIMALS. glandular walls ; then comes the gizzard, composed of two thick, red, striped muscles, covered internally with a thick, horny epithelium. The gastric parts of this class of birds are therefore divided into three sections—first, the crop, to act as a reservoir, in which the food is macer- ated ; from this it is pushed gradually into the second, the stomach, in which it undergoes gastric digestion simultaneously with the process of tritura- tion which occurs in the giz
. The physiology of domestic animals ... Physiology, Comparative; Veterinary physiology. 380 PHYSIOLOGY OF THE DOMESTIC ANIMALS. glandular walls ; then comes the gizzard, composed of two thick, red, striped muscles, covered internally with a thick, horny epithelium. The gastric parts of this class of birds are therefore divided into three sections—first, the crop, to act as a reservoir, in which the food is macer- ated ; from this it is pushed gradually into the second, the stomach, in which it undergoes gastric digestion simultaneously with the process of tritura- tion which occurs in the giz- zard, or the third digestive compartment (Fig. 154). Grains, etc., which form the food of gallinaceous birds, first go into the crop, which they distend, and in which the}- accumulate in consid- erable quantity. Here the food becomes softened and takes on an acid reaction. A comparatively profuse se- cretion is poured out in this pouch, whose properties have not been thoroughly investigated. By inserting substances into the crop, Spallanzani obtained one ounce of fluid in twelve hours from the crop of a pigeon, and seven ounces of the fluid from a guinea-hen ; but although this fluid is thus poured out in consid- erable amount, it does not appear to be very active in softening the food. It is not known that this secre- tion has any digestive prop- erties, although it seems probable that starch would here be converted into sugar, since grain remains in this compartment for twelve or thirteen hours, or even much longer. After leaving the crop, the food then passes into the ventriculus and gizzard. The ventriculus is supplied with a large number of tubular glands, which secrete an acid Fig. 154.—Crop and Stomach of the Pigeon. {Bernard.) MM, crop; I, oesophagus: C. proventrieulus ; S, tubular glands of stomach; J, gizzard; D. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - colorat
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