. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MONOTREMATA. 403 Fig. 198.. Mammary gland, Ornitharhynchns, nearly arrived at full size. ( Mcchd.) Geoffrey lias argued (Annales dcs Sciences Nut, ix. 1826, p. 457) that the subcutaneous abdominal glands considered by Meckel as mammary, possess none of the characters of a true mammary gland ; he states that he exa- mined them with the greatest attention, com- paring them with the human mammary glands, and especially with those of Marsupial animals, and that they were of a totally different texture, consisting of a vast n

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. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MONOTREMATA. 403 Fig. 198.. Mammary gland, Ornitharhynchns, nearly arrived at full size. ( Mcchd.) Geoffrey lias argued (Annales dcs Sciences Nut, ix. 1826, p. 457) that the subcutaneous abdominal glands considered by Meckel as mammary, possess none of the characters of a true mammary gland ; he states that he exa- mined them with the greatest attention, com- paring them with the human mammary glands, and especially with those of Marsupial animals, and that they were of a totally different texture, consisting of a vast number of cacums placed side by side, all directed to the same point of the skin, where only two excretory orifices were to be perceived, and these orifices so small that the head of the smallest pin could not be made to enter them. That above all there was no trace of nipples; that in the specimen examined by him, which had the size and ap- pearance of an adult female, the apparatus in question was not more than a fourth part the size of that observed by Meckel. But a mam- mary gland, Professor Geoffroy observes, when arrived at its full development, occasions an enlargement of all its constituent parts, the nipple acquiring additional bulk even before lactation commences, and that there was no appearance of this kind in the Ornitho- rhynchus. He considers, therefore, these ab- dominal glands as analogous to those which are situated along the flanks of Salamanders, and still more to the odoriferous glandular ap- paratus which is concentrated at the sides of the abdomen in the Shrews. In the absence of direct testimony of the nature of the secretion of the abdominal sub- cutaneous glands of the female Ornithorhyn- chus, the next obvious step was to test their disputed nature and office by an examination of their periods of increase and functional activity, as compared with those of the ovaria. If these glands had been analogous to the scent- glands of the flanks in the Shrews,