220 Veti-:rin.\r\ patiiolligv. 



Effects. — The effects of colloid accumulation depend upon 

 the extent of it. The exact function of the thyroid gland has not 

 been determined but it is quite certain that the iodine compound, 

 iodothvrein or thyroiodin is the active principle of the thyroid 

 secretion. It is not known whether the thyroid secretion has 

 some action vron cell metabolism or neutralizes various poison- 

 ous substances that result from metabolism or poisons intro- 

 duced into the body from without. The colloid accummulations 

 in giiitre contain less iodine per driven volume than the normal 

 secretion, but the total quantity of iodine is materially increased 

 resulting in circulato.ry disturbances, as rapid weak pulse, in- 

 creased metabolic activity especially of proteids, increased secre- 

 tions, irrital)ility, etc. Diminished iodine production, as ob- 

 served in my.\uedema, is not common in colloid accummulation. 



SEROUS INFILTRATION. 



DEFINITION. 

 ETIOLOGY— (Oedema). 

 APPEARANCE. 



Macroscopic. 



Microscopic. 

 TISSUE AEFECTED. 

 EFFECTS. 



Serous infiltration is a condition in which excessive quantities 

 of lymph or serous fluid infiltrates the cells. 



In the anatomo-physiologic discussion of the cell, the nutri- 

 ents were said to be obtained by specific selective action of the 

 cells and by osmosis. Osmosis is probably the most important 

 mode of passage of extracellular substances into the cell. 



In hydremia or other conditions in which cells are bathed by 

 excessive quantities of fluid, there is a tendency for them to 

 become hydropic. 



Serous fluid that enters the cells in serous infiltration is thin, 

 Avatery and contains small (|uantities of proteids and salts. 



Etiology. — The cause of serous infiltration is an excess of 

 serous fluids in the tissues. Serous infiltration is, therefore, an 

 accompanying condition of oedema and the causes of oedema 

 would likewise be the primary cause of serous infiltration. A 

 second cause may be the impairment of the cells in which they 

 are stimulated to imbibe more fluid. 



Appearance. — Macroscopis. — Because of the simultaneous 

 occurrence of oedema and cellular serous infiltration and in 

 view of the fact that oedema is so conspicuous, the serous infil- 

 tration is not recognizable in gross examination. 



