EETROc,Ri:ssr\i-: iissri-: chaxcks. 217 



COLLOID CHANGES. 



DEFINITION. 

 ETIOLOGY— Unknozm. 

 APPEARANCE. 



Macroscopic. 



Microscopic. 

 TISSUE AFFECTED. 



Thvroid, prostate, tumors. 

 EFFECTS. 



The term "Colloid" has rather an indefinite meaning and by 

 present day writers is used to indicate a variety of substances. 

 "The word colloid is merely morphologicallv and macroscop- 

 ically descriptive of certain products of cell activity or disinte- 

 gration, which have nothing in common except the fact that thev 

 form a thick glue like or gelatinous, often brownish or yellow- 

 ish substance" (Wells). One type of colloid substance is a 

 physiologic product of the thyroid gland, it is in part a secre- 

 tion of the thyroid cells and in part a conversion of those cells 

 into colloid material. This product is normally absorbed as it 

 is produced though it may accummulate in small cpiantitics in 

 the gland acini, especialh- in aged animals. 



Chemically the physiologic tliyroid colloid is composed of 

 iodo-thyreoglobulin (a compound of globulin and thyroidin). 

 Thj'roid colloid is glue like in consistency and varies in color 

 trom brown to yellow. Colloid and mucous are closely related. 

 Colloid does not increase in bulk when it is suspended in water, 

 neither is it precipitated bv alcohol or acetic acid — two tests that 

 are usually sufficient for differentiation of mucus and colloid. 

 Pseudo-mucin is more difificult to differentiate from colloid. The 

 latter, however, contains iodine and the former does not. 



Pathologic colloid changes are conditions resulting from the 

 excessive production and retention of collagenous material. The 

 disturbance induced by excessive colloid accummulation is usu- 

 ally not serious althougli it may cause fatal termination. This 

 condition occurs more frequently in old dogs than in other ani- 

 mals. Sheep occasionally show lesions of this condition, in 

 some instances the entire flock becoming affected. Pathologic 

 colloid accummulation is a constant lesion in the tliyroid gland 

 of animals suffering from exophthalmic goitre. Colloid changes 

 have been observed in cattle, sheep, horses, mules and one case 

 has been recently noted in a calf. 



Etiology. — The specific exciting cause of pathologic colloid 

 changes is not known but undue exposure to inclement weather 

 is a predisposing cause of considerable moment. Exposure, in 

 some instances, appears to become an exciting cause of thyroid 



