182 



NORMAL HISTOLOGY. 



the secreting cells as may be destroyed (Fig. 156). The colloid 

 material is produced within the cytoplasm of the secreting cells, 



FIG. 157. 



'^fM^^PHPHBI 



Section from thyroid of dog, illustrating the egress ot colloid from the alveoli. (Bozzi.) 

 a, epithelial cells lining the alveolus, seen in section. The internal ends of similar cells 

 are seen in superficial aspect below. 6, colloid within the alveolus ; c, exit of colloid 

 between two epithelial cells ; e, lymphatic vessel ; d, end of a colloid or secreting cell in 

 the epithelial lining of the alveolus. 



whence it is either expelled into the lumen of the alveolus, or the 

 whole cell becomes detached from the alveolar wall and suffers col- 



FIG. 158. 



Section from thyroid of dog, illustrating the egress of colloid from the alveoli. (Bozzi.) 

 a epithelial lining of the alveolus ; b, colloid ; c, escape of colloid through a defect in the 

 wall occasioned by the colloid metamorphosis of some of the epithelial cells, the nuclei 

 of which are discernible within the colloid near c. 



loid degeneration, with destruction of the nucleus, within the 

 alveolar cavity. 



