MAMMARY GLANDS. 



251 



Although the usual number of mammae in 

 the human species is only two, still there 

 are exceptions and instances on record of 

 more having been developed. One of the 

 best authenticated and most recent of these 

 cases is related by Dr. Lee, in the Transac- 

 tions of the Medical and Chirurgical Society 

 for 1837.* 



In this instance " the inferior or pectoral 

 mammae were fully developed and in the na- 

 tural situation, and their nipples, areolae, and 

 glands presented nothing unusual in their ap- 

 pearance. Near the anterior margin of the 

 axilla, a little higher up on each side, was si- 

 tuated another mamma, about one-sixth of the 

 size of the others. The nipples of these were 

 small and flat, but when gently pressed, a 

 milky fluid which had all the external cha- 

 racters of the milk secreted by the other breasts, 

 flowed copiously and readily from several ducts 

 which opened on their extremities. When 

 milk was drawn from the lower breasts, a small 

 quantity usually escaped from the nipples of 

 the superior breasts, and when the draught 

 came into the former, the latter invariably be- 

 came hard and distended.'' The flatness of 

 the nipples prevented her suckling her children 

 by them. Dr. Lee, in the above paper, quotes 

 five other cases from foreign authors of qua- 

 druple mamma, also stating that " in some 

 women only one breast has been developed ; 

 others have had two nipples placed on one 

 mamma; and a few individuals have had three 

 breasts, two in the natural situation and a third 

 situated in the middle of the two others. Only 

 one case has been recorded of five mammae in 

 the human subject."f 



Comparative anatomy. In considering this 

 division of our subject we shall especially di- 

 rect our attention to those points in the anatomy 

 of the mammae of animals which possess a phy- 

 siological interest, omitting minute anatomical 

 details unless they bear upon general principles. 

 These organs in the Kangaroo, one of the Mar- 

 supiata, as we have already hinted at, are 

 peculiarly formed, for the young of these ani- 

 mals,when first removed from the uterine cavity 

 of its parent, is more like an earth-worm in its 

 appearance than the active animal by which 

 it is produced. So helpless is the condition of 

 this young animal that it has not been inap- 

 propriately called a mammary fatux, for the 

 mamma?, in this instance, act at first like a true 

 placenta as a permanent conductor of nutri- 

 ment, and not, as in the higher Mammalia, 

 a mere storehouse to be resorted to occasionally. 

 Indeed, so close is the union between the pa- 

 rent and its offspring, and so imperfect the 

 power of the foetus to abstract nourishment by 

 suction, that Geoffrey St. Hilaire had recourse 

 to the hypothesis that there was some vascular 

 connexion. But the imperfect power of the 

 foetus is compensated by the addition to the 

 breast of a muscular apparatus, which propels 

 forwards the nutritious juices of the mother 

 into the alimentary cavity of the helpless 



* Page 266. 



t Diet, des Sciences Mcd. torn, xxxiv. p. 529. 



young one. From the interesting account 

 which Mr. Morgan has given of these glands* 

 in the Kangaroo, we shall extract the following 

 particulars. 



In this animal there are four teats, two of 

 which, in the virgin state, are at the bottom of 

 a narrow pouch in which they lie hid. It is to 

 one of these teats that the marsupial foetus is 

 attached immediately after its removal from the 

 uterus, and their size, at first small in accord- 

 ance with the minute mouth of the animal, in- 

 creases with its growth. The muscular appa- 

 ratus above alluded to embraces both the teat 

 and the gland, and acts from the marsupial as 

 its fixed point. The teat is further provided 

 with a true vascular erectile tissue. 



The upper or smaller gland is perfectly 

 similar in its organization to the larger, and, 

 notwithstanding the doubts which Mr. Morgan 

 expresses regarding its use, Mr. Owen observed 

 in the instance which he has so carefully re- 

 corded in the Philosophical Transactions for 

 1834, that the foetus was attached to the upper 

 and not the lower nipples, and " that the 

 nipple in use by the young one of the previous 

 year was the right superior or anterior one." 

 With regard to their minute structure it would 

 appear from the figures of Mr. Morgan that the 

 lacteal tubes originate in plexuses and not in 

 cells, but the text is not very precise on this 

 point. 



The consideration of the existence of these 

 organs in those bird-like Mammalia, the Orni- 

 thorhynchi, or duck-billed moles of Australia, 

 is interesting. For the beak-bearing mouth of 

 the adult would not lead us to expect the ex- 

 istence of a gland, the secretion of which is 

 usually obtained by the action of a soft mouth 

 convertible into a sucking apparatus. 



Nevertheless a distinct mammary gland was 

 described and figured by Meckel in 1826; and 

 an organization of the lips and tongue of the 

 young animal to correspond with it was sub- 

 sequently described by Professor Owen in the 

 Trans. Zool. Society, vol. i. p. 228, 1834. 



According to Meckel this gland is placed 

 on the side of the abdomen between the pan- 

 niculus carnosus, to which it adheres loosely, 

 and the obliquus descendens abdominis,stretch- 

 ing from the anterior and external margin of 

 the pectoral muscle and inferior extremity of 

 the sternum to the thigh. Its great size is 

 merely one among the many instances which 

 we meet of the comparative want of con- 

 centration of individual organs in the lower 

 as contrasted with the higher animals, for the 

 secreting surface itself is much less extensive 

 than in those animals in whom the whole organ 

 is much less. 



The mammary glands of the Ornithorhyn- 

 chus are peculiar for the absence of the nipple, 

 a deficiency which is not met in any other 

 class. In the Cetacea it is so completely bu- 

 ried and concealed that it has been described 

 as absent, but it exists perfectly formed, 

 buried in its protecting fissure. The defi- 

 ciency in the first and concealment in the last 



* Linn. Trans, vol. xvij. 1828. 



