332 EPITHELIAL AND ENDOTHELIAL TISSUE. 



understand the weakening of the whole organism by diarrhoea, 

 the relief afforded by drastics in certain diseases, etc. 



(c) The fatty secretion can be best studied under the micro- 

 scope in colostrum corpuscles, which are suspended in the serous 

 discharge of the mammary glands for a few days after delivery. 

 Here we see the first-formed fat-granules still in connection with 

 the net-work of the living matter within the plastid, and w r e 

 arrive at the conclusion that fat is a directly transformed living 

 matter (see page 28). During the active locomotion of a colos- 

 trum corpuscle, very often fat-granules are thrown up from its 

 interior (S. Strieker). After a few days, however, no more 

 colostrum corpuscles are secreted, because the living matter of 

 the epithelia is nearly completely transformed into fat-granules, 

 leading to a continuous destruction of the epithelia, the granules of 

 which commingle with a serous fluid and form the emulsion called 

 milk. This process of fatty change in the living matter of the 

 epithelia of the mammary glands is a remarkably rapid one. In 

 microscopic specimens of a breast from the corpse of a nursing 

 woman, we find in the secretory epithelia little unchanged bio- 

 plasson, the greater part of it being transformed into fat- 

 granules. If these be extracted from the specimen with oil of 

 cloves, only the shells of the cement-substance of many of the 

 epithelia are left behind. Through what agencies the enormously 

 augmented bioplasson becomes transformed into fat is at pres- 

 ent not understood. There is no doubt, however, that this 

 material is an offspring of the epithelia. Those who claim that 

 the new material for the formation of milk are " leukocytes," 

 or emigrated colorless blood-corpuscles, are in the dark regard- 

 ing the nature and the function of epithelia and glands. The 

 serous liquid in which the small fat- granules of the milk are 

 suspended evidently comes from the blood-vessels ; for it is well 

 known that abundant drinking increases the quantity of milk. 

 The amount of milk furnished by one udder, in the act of milk- 

 ing, greatly exceeds the volume of the udder, which indicates 

 that a continuous flow of the plasma of blood takes place during 

 the milking process. Toward the end of milking, the plasma 

 being exhausted, very rich, inspissated milk is obtained. 



The highest degree of fatty change of the bioplasson is 

 reached in the sebaceous and the ceruminal glands. The won- 

 derful apparatus for the extrusion of the fat from the sebaceous 

 glands will be spoken of in the chapter on the skin. 



