CONDITIONS OF INFILTRATION. 



41 



ment. The substance then assumes more of a viscid character, 

 and finally becomes quite fluid. The ultimate chemical product 

 of colloid metamorphosis is, like that of mucous softening, sodic 

 albuminate ; its morphological result is either a single, smooth- 

 walled cyst, or a complete system of intercommunicating cysts, 

 the so-called " alveolar structure." 



To understand this we must remember that in the patholo- 

 gical development of colloid matter (colloid cancer) a great 

 number of colloid foci originate in close proximity to one 



another. 



Fig. 13. 



Section from a colloid or alveolar cancer 



The matrix of the connective tissue in which they originate 

 suffices for a while to keep the individual colloid granules apart ; 

 but as their size increases, the partitions between them waste, 

 the partial or complete fusion of neighbouring cavities resulting 

 in an irregular, loculose sul)division of the disposable space, which 

 may very fairly be compared to the alveolar structure of the 

 pulmonary parenchyma (fig. 13). (Cf. the section on Colloid 

 Cancer.) 



3. Conditions of Infiltration. 



§ 45. The degenerations which come under this head are less 

 worthy to be called '' retrograde metamorphoses " than those 

 which we have hitherto discussed. 



The affected structures retain their external form even in 

 advanced stages of morbid change ; they retain it, that is, to such 



