. Milk. Milk. THE PHYSIOLOGY OF LACTATION 47 placed in the aperture of the teat, thus opening it slightly and facilitating the release of milk. In other cases a surgical opera- tion becomes necessary, by which the muscle is cut and weakened sufficiently to render milking less difficult. The skin of the teat has neither hair nor sweat-glands, and the mucous membrane which fines the teat duct expands in the cistern. The cistern, therefore, may be regarded as the expansion of the teat duct (Fig. 13). The cistern (sinus lactiferus) is a pouch which is sepa- rated from the teat by a circular muscle
. Milk. Milk. THE PHYSIOLOGY OF LACTATION 47 placed in the aperture of the teat, thus opening it slightly and facilitating the release of milk. In other cases a surgical opera- tion becomes necessary, by which the muscle is cut and weakened sufficiently to render milking less difficult. The skin of the teat has neither hair nor sweat-glands, and the mucous membrane which fines the teat duct expands in the cistern. The cistern, therefore, may be regarded as the expansion of the teat duct (Fig. 13). The cistern (sinus lactiferus) is a pouch which is sepa- rated from the teat by a circular muscle, over which the cow has fittle control. This cistern is of variable size and may contain from less than | pint to 1 pint of milk. It is connected with other parts of the udder by a network of milk-ducts whose lumen is largest at the point where it opens into the cistern. These ducts. a Fig. 13.—a, Upper end of teat duct; b, cistern. (Ernst.) anastomose and end in the ultimate folficles or gland lobules. Anastomosis is more pronounced in the upper regions of the udder than near the cistern. The upper parts of the two quarters of the udder that belong to the same gland are connected by these milk-ducts, so that communication is established. At the junc- ture of the milk-ducts there are small cisterns and a system of sphincter muscles protects all junctures of the ducts. These sphincter muscles are under control of the cow and enable her to withhold milk at will, or perhaps by an involuntary reflex, so that, when she suffers from nervousness caused by disease, maltreat- ment, or dislike of the milker, she is able to hold up the greater part of the milk. Such conditions frequently interfere with the productiveness of a cow and are difficult to Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Heineman
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Keywords: ., bookauthorheineman, bookcentury1900, bookdecade1910, bookyear1919