184 



THE ESSENTIALS OF HISTOLOGY 



activity, the cells of the alveoli become much enlarged and of a columnar 

 shape, and fatty globules become formed within them (B). These fatty 

 globules appear to become set free by the breaking down of the inner part 

 of the cell, the protoplasm of the cells becoming partially dissolved and 



FIG. 220. ALVEOLI OF THE MAMMARY GLAND OF THE* BITCH UNDER DIFFERENT 



CONDITIONS OF ACTIVITY. 



A, section through the middle of two alveoli at the commencement of lactation, the 

 epithelium-cells being seen in profile ; B, an alveolus in full secretory activity. 



forming the proteid substances of the milk. According to some authors, 

 lymph-corpuscles may also carry fat into the alveoli and there become 

 disintegrated. At the commencement of lactation this disintegration 

 is imperfect, so that numerous cells containing fat-particles appear in 

 the secretion (colostrum corpuscles). 



