274 SPECIAL HISTOLOGY. 



The nipple (mamilla) and the areola, present numerous 

 smooth muscles, to which the contractility of those parts is 

 owing (vid. § 34) ; a delicate cuticle, the horny layer of which, 

 in the female, is not more than O'OOG'" thick, whilst the Mal- 

 pighian layer has a thickness of 0-04'" and is coloured in the 

 deeper portion; and compound papilla ± — &'" long. On the 

 breast itself, the papillae are small (^ — ^") and simple, and 

 the epidermis still finer (0032 — 0*04 /// ), although with a 

 thicker horny layer of 0*02 — 0-024"'. In the areola, especially 

 at its borders, but not on the nipple itself, there are large 

 sudoriparous glands, often with peculiar contents, and large 

 sebaceous follicles with fine hairs, which frequently form 

 little papilla, visible on the exterior {vid. §§68 and 73). In 

 the male, I have seen sebaceous glands without hairs, also on 

 the nipple. 



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

 surround the gland-vesicles with a rather close plexus of capil- 

 laries. The veins in the areola constitute a circle, which is 

 not always quite complete {cir cuius venosus Halleri). The 

 lymphatics are equally abundant in the skin covering the 

 gland, whilst in the gland itself they have not yet been 

 demonstrated. The nerves of the skin covering the mamma 

 are derived from the supraclavicular nerves, and the cutaneous 

 branches of the second, third, and fourth intercostals. In the 

 interior of the gland, no other nerves can be traced than a few 

 fine twigs accompanying the vessels, whose termination is 

 unknown. 



At the time of lactation the gland enlarges very considerably. 

 Its tissue is no longer uniform, whitish, and firm, but softer, 

 granular, and lobate, with a yellowish -red, glandular paren- 

 chyma, distinctly bounded by the whitish, spongy interstitial 

 tissue. The gland-vesicles and lactiferous ducts are wider, 

 filled with milk, and the vessels excessively multiplied. In 

 the external parts, the enlargement of the areola and of the 

 nipple is especially worthy of remark ; the cause of which ap- 

 pears to depend upon a growth of these parts, with all their 

 elements, including the muscular fibres and minute glands ; 

 and not in a simple extension of the colour over a larger sur- 

 face. In the male, the lacteal gland is quite rudimentary, 

 J — 2" broad, and 1 — 3'" thick, not lobed, and firm. The 



