146 



MAMMARY GLANDS. 



they are emigrated lymph-corpuscles ; while still a third regards 

 them as derived from the wandering cells of the connective tissue. 

 When the period of lactation is over the glands return approxi- 

 mately to their original condition, thus undergoing the process of 

 involution. 



Clavicle. 



Greater pectoral 

 muscle. 



Integument- 



Fibrous septa con- 

 nected with in- 

 tegument. 

 Glandular tissue. 



Mass of adipose 

 tissue. 



Areola., 



Interlobular adi- 

 pose tissue. 



Nipple. 



Lactiferous duct..} 



Ampulla. 

 Interlobular adi- 

 pose tissue. 

 Glandular tissue. 



Peripheral acini 



Mass of adipose 

 tissue. 



Fibrous septa. 

 Integument. 



First rib. 



Second rib. 



Lesser pectoral 

 muscle. 



Intercostal mus- 

 cles. 



Third rib. 

 Deep fascia. 



Superficial fas- 

 cia. 



Fourth rib. 



Horizontal axis 

 of nipple. 



Fifth rib. 



Sixth rib. 



External oblique muscle. ' 



FIG. 88. Longitudinal section of mammary gland in situ; frozen subject of twenty 



years (Testut). 



That the secretion of milk is under the control of the nervous 

 system there is no doubt, for the instances are numerous in which 

 strong emotions of grief or anger have caused the secretion to 

 cease, but just what the relation is remains still undecided. It 

 may be that secretory nerves are involved in the activity of these 

 glands, or that it is through the influence of vasomotor fibers that 



