MAMMARY SECRETION 289 



color and about the consistence of honey, becoming darker and more 

 viscid on exposure to the air. It has a decidedly bitter taste. It readily 

 forms a sort of emulsive mixture with water. 



Examined microscopically, the cerumen is found to contain semisolid 

 dark granules of an irregularly polyhedric shape, with epithelium from 

 the sebaceous glands, and epidermic scales, both isolated and in layers. 

 Sometimes, also, a few crystals of cholesterin are found. 



Chemical examination shows that cerumen is composed of oily 

 matters fusible at a low temperature, a peculiar organic matter resem- 

 bling mucin, with sodium salts and a certain quantity of calcium phos- 

 phate. The yellow coloring matter is soluble in alcohol; and the residue 

 after evaporation of the alcohol is soluble in water and may be precipi- 

 tated from a watery solution by neutral lead acetate or tin chloride. 

 This extract has a bitter taste. 



The cerumen lubricates the external meatus, accumulating about the 

 hairs in the canal. Its bitter taste is supposed to be useful in preventing 

 the entrance of insects. 



Meibomian Secretion. Little is known concerning any special prop- 

 erties of the Meibomian secretion except that it mixes in the form of an 

 emulsion with water more readily than the other sebaceous matters. It 

 is produced in small quantity, mixed with mucus and the secretion from 

 the sebaceous glands attached to the eyelashes and the glands of the 

 caruncula lachrymalis, and smears the edges of the palpebral opening. 

 This oily coating on the edges of the lids, unless the tears are produced 

 in excessive quantity, prevents their overflow upon the cheeks, and the 

 excess is carried away by the nasal duct. 



MAMMARY SECRETION 



The mammary glands are among the most remarkable organs in the 

 economy ; not only on account of the peculiar character of their secre- 

 tion, which is unlike the product of any other of the glands, but from 

 the changes which they undergo at different periods, both in size and 

 structure. Rudimentary in early life and in the male at all periods of 

 life, these organs are fully developed in the adult female only in the 

 later months of pregnancy and during lactation. In the female, after 

 puberty, the mammary glands undergo a rapid increase in size ; but 

 even then they are not fully developed. 



Physiological Anatomy of the Mammary Glands. The form, size 

 and situation of the mammae in the adult female are too well known to 

 demand more than a passing mention. These organs are almost invari- 

 ably double and are situated on the anterior portion of the thorax, over 



