5i8 Veterinary Medicine. 



Presence of Colloids. This may be found in the presence 

 of solid or semi-solid particles. Just as the introduction of a 

 thread into a concentrated solution of sugar or salt will induce 

 an instant crystallization on the filament so the presence of solid 

 bodies determines a similar condensation in solid form of the 

 solids of the bile. But this tendency is increased materially if 

 the solid body is itself of a colloid or non-crystallizable material. 

 Rainey and Ord have shown experimentally that colloid bodies 

 like mucus, albumen, pus, blood, epithelial cells, not only de- 

 termine the precipitation of crystallizable salts from a strong 

 solution, but that they cause the precipitate to assume the form of 

 globular or spherical particles, which by gradual accretions on 

 their surfaces tend to grow into calculi. They found that salts 

 which are deposited by mere chemical reaction, without the in- 

 tervention of colloids, appear in the form of sharply defined 

 angular crystals. The very fact that a precipitate assumes a 

 spherical form suggests the presence of colloids as an active factor 

 in the precipitation. Heat appears to intensify this action, though 

 probably the normal body temperature operates mainly through 

 the more active proliferation of bacteria. 



Bacteridian infection. In connection with the action of colloids 

 it has been observed that when such bodies are in a condition of 

 fermentation they are much more potent as precipitants than if in- 

 active and sterile. But as all fermentations are the work of 

 microorganisms we are at once brought to the conclusion that 

 bacterial infection is one of the most potent causes of calculous 

 formations. The invading microbes operate upon the dissolved 

 solids, causing changes in their condition which reduce their 

 .solubility, and thus determine the .separation of calculi and con- 

 cretions in a manner allied to the precipitation of nitrates in the 

 soils. 



But the same microbes operate in producing the colloids which 

 cooperate .so effectively in the formation of calculi. The catarrh- 

 al biliary ducts, or bladder, shed their epithelium, and transude 

 white and red globules, and torni pus and an excess of mucus, all 

 tending to the separation of the biliary solids or forming nuclei 

 on which these solids may condense. The calculi and concretions 

 tend in their turn to maintain and advance the inflammation. 



The access of the microbes to the biliary duct or bladder may 



