MAMMARY GLANDS SECRETION OF MILK. 



647 



of Oil of Turpentine, and probably of other volatile agents, is produced much 

 rapidly; the characteristic odour of violets being perceptible in the 



more 



Urine passed but a few minutes after the vapour of the oil had been received 

 into the lungs. 



4. Mammary Glands. Secretion of Milk. 



853. We now come to those Glands, whose action is rather to elaborate 

 from the Blood certain products, which are destined for special uses in the 

 economy, than to eliminate matters, whose retention in the circulating current 

 would be injurious. Pre-eminent amongst these in size and importance, at 

 least during their period of activity, are the Mammary Glands ; which are 

 found only in the animals of the Class Mammalia, and which present them- 

 selves in an almost rudimentary state in some of the non-placental subdivisions 

 of the class ( 44). 



a. The structure of the Human Mammary Gland, which has been recently investigated 

 fully by Sir A. Cooper, is very simple, and easily described. It consists of a series of ducts 

 passing inwards from their termination in the nipple, and then ramifying like the roots of a 

 tree, their ultimate subdivisions terminating in minute follicles. The mamillary tubes are 

 usually about ten or twelve in number; they are straight ducts, of somewhat variable size; 

 and their orifices, which are situated in the centre of the nipple, and are usually concealed 

 by the overlapping of its sides, are narrower than the tubes themselves. At the base of the 

 nipple, these tubes dilate into reservoirs, which extend beneath the areola and to some dis- 

 tance into the gland, when the breast is in a state of lactation. These are much larger in 

 many of the lower Mammalia than they are in the Human female; their use is to supply 

 the immediate wants of the child when it is first applied to the breast, so that it shall not 

 be disappointed, but shall be induced to proceed with sucking until the draught be occasioned 

 ( G'26). From each of these reservoirs commence five or six main branches of the lacti- 

 ferous tubes, each of which speedily subdivides into smaller ones; and these again divari- 

 cate, until their size is very much reduced, and their extent greatly increased. The propor- 

 tional size of the trunk and of its branches, appears to follow the same law which governs 

 that of the blood-vessels. The breast is not formed into regular lobes by the ramifications 

 of the ducts; because they ramify between, and intermix with each other so as to destroy 



[Fig. 251. 



\ 



The Mammary Gland after the removal of the 

 skin, as taken from ihe subject three days after 

 delivery ; 1, the surface of the chest ; 2, subcuta- 

 neous fat ; 3, the skin covering the gland ; 4, cir- 

 cumference of the gland; 5, its lobules separated 

 by fat; 6, the lactiferous ducts converging to unite 

 in the nipple; 7, the nipple slightly raised and 

 showing the openings of the tubes at its extremity.] 



A vertical section of the Mammary Gland, 

 showing its thickness and the origins of the lacti- 

 ferous ducts ; 1, 2, 3 its pectoral surface ; 4, section 

 of the skin on the surface of the gland; 5, the thin 

 skin covering the nipple ; 6, the lobules and lobes 

 composing the gland ; 7, the lactiferous tubes com- 

 ing from the lobules; 8, the same tubes collected 

 in the nipple.] 



