For exploring the mechanism of toxic effects on the aquatic caused by mercury

it has been carriedout a toxical experiment with tadpoles of Bufo viridis Laurenti by mercuric chloride (HgCl2)

having ob-servation of continuous paraffin sections

H.E colouring normal histology and pathohistology of wholebody.After comparation

the remarkable changes of organs or tissues by mercury treatment has beendiscovered.1.Liver:hyperaemia

swelling of hepatocytes and reduction of hepatic sinusoids appeared.2.Pronephros (Kindney):the cells of renal tubules swelled

there were a lot of glue—like parti-cles in the cytoplasms and some of cells broke.3.Neural Tube:a part of neurons died or distintegrated.4.Intestine:the epithelial cell layer of intestine separated from serosa to form a series of empty cavities.5.Heart:malformation of ventricle and hyperplasia of cardiac muscles occured.The toxic action of mercury may result from that the heavy metal binds sulfhydryl group(—SH)of proteins or enzymes and finally inhibits functions of cells.