. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. 122 COMPARATIVE ZOOLOGY. be poured. Usually, however, the cells of the membrane manufacture the secretion from materials furnished by the blood. Even in the higher animals, there are such secret- ing membranes. The membranes lining the nose and ali- « 5 mentary canal and enclosing the lungs, heart, and joints, secrete lubricating fluids. The infolding of such a membrane into little sacs or short tubes (follicles), each having its own outlet, is the type o
. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. 122 COMPARATIVE ZOOLOGY. be poured. Usually, however, the cells of the membrane manufacture the secretion from materials furnished by the blood. Even in the higher animals, there are such secret- ing membranes. The membranes lining the nose and ali- « 5 mentary canal and enclosing the lungs, heart, and joints, secrete lubricating fluids. The infolding of such a membrane into little sacs or short tubes (follicles), each having its own outlet, is the type of all secreting and ex- <? , , â creting organs. The lower tribes have nothing higher, and the apparatus for pre- paring the gastric fluid at- tains no further develop- ment even in Man. When Fig. plans of secreting Mem- a cluster of these f ollicleS, Or branes. The heavy line represents the areolar-vascular layer; the next, line is saCS, discharge their Contents the basement, or limiting membrane; and the dotted line the epithelial layer: by One COmmOU dllCt, WG a shows increase of surface by simple i â iâ j ±u plaited or fringed projections; *, Ave haVe a 9land- But whether modes of increase by recesses, forming metnbrane, follicle, Or gland, simple glands, or follicles; c, two forms 7 0 of compound glands. the organ is covered wTith a net-work of blood-vessels, and lined witli epithelial cells, which are the real agents in the process. The chief Secreting Organs are the salivary glands, gastric follicles, pancreas, and liver, all situated along the digestive tract. 1. The salivary glands, which open into the mouth, se- crete saliva. They exist in nearly all Vertebrates, higher Mollnsks, and Insects, and are most largely developed in such as live on vegetable food. The saliva serves to lu- bricate or dissolve the food for swallowing, and, in some Mammals, aids also in digestion of Please note that these images are extracted from scanned p
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1883
