醫(yī)學(xué)英語(yǔ)中經(jīng)常出現(xiàn)這樣的句型：

It is+ necessary, important, essential, crucial 等(表示重要性和必要性的形容詞）+that引導(dǎo)的主語(yǔ)從句，或It is+preferable，advisable等(表示“適當(dāng)”“可取”意義的形容詞）+that引導(dǎo)的主語(yǔ)從句。

這類句型的that從句中，謂語(yǔ)一般都用should加動(dòng)詞原形，這是一種虛擬語(yǔ)氣，幫助構(gòu)成虛擬語(yǔ)氣的助動(dòng)詞should?？墒÷圆挥?，而直接使用原形動(dòng)詞。因此，that從句中可能出現(xiàn)類似he (should) have的主謂形式，要避免錯(cuò)誤理解。

上述句型可按一般主語(yǔ)從句翻譯，that從句中的should有時(shí)需譯為“應(yīng)該”有時(shí)也可省略不譯。

虛擬語(yǔ)氣的主語(yǔ)從句譯例：

1. It is important that a careful examination be made of the patient's stomach.

重要的是應(yīng)該對(duì)病人的胃作仔細(xì)的檢査。

2. It is necessary that the patient be isolated to protect him from exposure to bacterial infection.

必須隔離患者使其不接觸細(xì)菌感染。

3. It is important that the malignant tumour be removed as thoroughly as possible in surgery to avoid its metastasis and recurrence.

重要的是手術(shù)時(shí)惡性腫瘤的切除應(yīng)盡可能徹底，以避免轉(zhuǎn)移和復(fù)發(fā)。

4. It is essential that we should have some knowledge about cancer.

我們應(yīng)該具備一些癌癥方面的知識(shí)，這是很必要的。

5. It is preferable that the patient have the test done before breakfast.

病人最好在早餐前做試驗(yàn)。

6. If one has a special medical condition, such as diabetes, epilepsy, or allergy, it is advisable that he carry some kind of identification in order to avoid being given improper medication in an emergency.

患有糖尿病，癲癇，變應(yīng)性疾病等特殊病癥的人最好攜帶某種識(shí)別證明，以免在緊急情況下醫(yī)生投用不適當(dāng)?shù)乃幬铩?/p>