472 OF THE LACTEAL GLAND. [sect. 209. 



77. Meckel, believe they have recently observed longitudinal muscular 

 fibres in the lacteal ducts ; not in those of the nipple, but deeper 

 in the gland. 



The nipple and the areola possess numerous smooth muscular 

 fibres, to which they owe their contractility {vide § 36) ; a delicate 

 epidermis, whose horny layer, in the female, measures only 0006"' 

 in thickness, while the Malpighian layer is 0*04'" thick, and co- 

 loured in the deeper portions; and compound papilla 3 -, -fa'" to - 3 V" 

 in height. On the breast itself, the papillae of the skin are small 

 (-^0'" to sV") and simple, and the epidermis is still thinner (o - o32 w 

 to 0-04'"), though the horny layer of it is of greater thickness, 

 measuring o*02'" to o , 024'". In the areola, especially at its border, 

 but not on the nipple itself, there occur large sudoriparous glands, 

 often with peculiar contents, and large sebaceous glands, in con- 

 nection with fine hairs ; these glands often form small prominences, 

 visible externally {vide §§67 and 73). In man, I have observed 

 sebaceous glands upon the nipple also, but without hairs. 



The blood-vessels of the lacteal glands are numerous, and sur- 

 round the gland-vesicles with a pretty close network of capillaries. 

 The veins in the areola form a circle, which is not always quite 

 complete [circulus venosus Halleri) . — The lymphatics are also very 

 abundant in the skin which covers the gland, but they have not 

 yet been demonstrated in the gland itself. — The nerves of the skin 

 which covers the mamma come from the supra-clavicular nerves, 

 and the cutaneous branches of the second to the fourth intercostal 

 nerves. No nerves can be traced into the interior of the gland, 

 except some fine branches running with the vessels, the termination 

 of which is unknown. 



The lacteal gland enlarges very considerably at the period of 

 lactation. Its tissue is no longer uniform, whitish, and firm, but 

 becomes softer, granular, and lobulated, and the reddish-yellow 

 granular parenchyma is distinctly marked off from the lax, whitish, 

 interstitial tissue. The gland-vesicles and lacteal ducts are now 

 wider and filled with milk, while the vessels are greatly increased 

 in number. In the external parts, the enlargement of the areola 

 and nipple is more especially worthy of notice, a phenomenon 

 which seems to depend upon a true growth of these parts with all 

 their elements, including the muscular fibres and the small glands, 

 and not upon a simple distribution of the colour over a larger 

 surface. — In the male, the lacteal gland is quite rudimentary, from 

 half to two inches broad, and 1 to 3 lines thick, firm and without 

 lobules. The lacteal ducts are destitute of the sinus lactifevi, and 



