英语语法分析

More probable is bird transport, either externally, by accidental attachment of the seeds to feathers, or internally, by the swallowing of fruit and subsequent excretion of the seeds.

更有可能的是鸟类运输：或者是通过外部途径，即种籽偶然附着在羽毛上；或者是通过内部途径，即鸟类吞食果实并随后将种籽排泄出来。

The excretion of methyl mercury becomes very difficult because of high enterohepatic circulation and reabsorption by proximal convoluted tubule.

由于甲基汞在体内的肠肝循环和肾脏近曲小管对甲基汞的重吸收效率高，使甲基汞的体外排泄十分困难。

Chronic exposure to Cd mainly causes the renal proximal tubule damage, which represents that the excretion of proteinuria, glucosuria and aminoaciduria.

慢性接触镉主要引起肾小管损伤，表现为蛋白尿、糖尿和氨基酸尿。