382 



MANUAL OF PHYSIOLOGY. 



But these colostrum corpuscles soon cease to be thrown off in 

 the secretion, and the saccules of the glands during active lacta- 

 tion do not contain any sign of the debris of cast-off cells, or any 

 gradations in degeneration. Only one row of finely granular 

 cells is found lining the saccules, and the cavities are filled with 

 globules of various sizes. From this it would appear that in the 

 earlier stages of the production of the secretion, the mammary 

 cells, after a long period of inactivity, are so unaccustomed to the 

 duty they are called upon to perform, that they succumb in the 

 effort, and, being unable to produce the rich secretion and retain 



FIG. 169. 



Section of the Mammary Gland of 

 a Cat in the early stages of lactation. 

 (A) Cavity of alveoli filled with 

 granules and globules of fat. 1, 2, 

 3. Epithelium in various stages of 

 milk formation. 



Cells of Mammary Gland 

 during lactation, stained 

 with osmic acid, so as to 

 show the various sized oil 

 globules as black masses. 

 (Cadiat.) 



their vitality, they are cast off. Their offspring, however, after a 

 generation or two acquire the necessary faculty of making within 

 their protoplasm all the necessary ingredients of the milk, and 

 discharge them out into the lumen of the saccules without them- 

 selves undergoing any destructive change. 



The influence of the nervous system on the secretion of the mam- 

 mary glands is distinctly shown by the wonderful sympathy 

 between the action of these glands and the conditions of the 

 generative apparatus. Further, different emotions have an effect, 

 not only on the quantity, but also on the quality of the secretion. 



