494 MAMM2E. 



radiated manner from the circumference to the centre, and 

 terminate on the surface of the nipple.* 



They are commonly about fifteen in number, and vary con- 

 siderably in size : the largest of them being more than one-sixth 

 of an inch in diameter.f 



Fig. 126.J 



They can be very readily injected by the orifices of the nip- 

 ple from a pipe filled with mercury, in subjects who have died 

 during lactation or pregnancy ; but they are very small in sub- 

 jects of a different description. 



It has been asserted by respectable anatomists, that these 

 ducts communicate freely with each other; but they do not 

 appear to do so ; each duct seems to be connected with its pro- 

 per branches only.<$> 



* Described in the 10th century, by Charles Etienne, Vesalius and Posthius, 

 but their uses were unknown. H. 



f These ducts vary in number in different individuals, from fifteen to 

 twenty. p. 



$ Fig. 126, is a vertical section of the mammary gland of a young female 

 who died during lactation. The ducts were injected with wax, and two dissected 

 out their full length to their origin in the lobules of the gland. 2, 2, Base of 

 the nipple. 3, 3, 3, Lactiferous ducts cut off at the base of the nipple. 4, 4, 

 The top of the ducts exhibited their whole length. 5, 5, Sinuses formed by 

 these ducts at the base of the nipple. 6, 6, 6, 6, Branches of these ducts 

 running to the lobules. 7, 7, 7, 7, 7, The lobules separated from each other. 

 8, 8, The orifices of these ducts on the top of the nipple. 



See Edinburgh Medical Commentaries, vol. i. p. 31. A paper by Meckel. 



