SECRETIONS in 



also reflexly when foreign substances irritate the conjunctiva 

 and by strong light falling upon the eye. 



The secretory nerves pass through thejachrymal nerve, 

 the subcutaneous mallar nerve, and the cervical sym- 

 pathetic. 



The tears flow through the ducts of the lachrymal gland 

 in the outer canthus of the eye into the conjunctival sac in 

 the inner canthus and thereby moisten the cornea and the 

 conjunctiva and remove foreign bodies out of the conjunc- 

 tival sac. 



In the inner canthus of the eye the tears are taken up by 

 the puncta lachrymale of the caruncula lachrymalis and then 

 flow through the nasal duct into the inferior meatus of the 

 nose. 



11. MILK SECRETION 



I. Composition of milk. Milk is a white opaque fluid 

 having an amphoteric reaction, a sweet taste, and a specific 

 gravity of 1.0281.034. It is an emulsion of fat in which 

 the fat droplets, of 1.5-5^ diameter, are surrounded by 

 pellicles of caseinogen. 



The white color and the opaqueness of milk are due to 

 the fact that the light is totally reflected by the fat droplets. 



Milk contains 13$ solids. The milk of young women 

 contains more solids than that of older women. The solids 

 are: 



(a) Proteids (2.5$), chiefly the nucleo-proteid caseinogen. 

 This proteid is split up by rennin into paracasein a pro- 

 teid which forms with calcium salts an insoluble double salt 

 (casein) and a soluble proteid (whey proteid). 



Besides the caseinogen, the milk contains, in smaller 

 quantities, two proteids which are coagulated by heat: 

 lactalbumin and lactoglobulin. 



(b) Carbohydrates (6#), namely, milk-sugar or lactose 

 (see page 21). When milk stands for a long time the lac- 

 tose undergoes lactic-acid fermentation (due to bacterium 



