物质的自由运动形成扩散现象、扩散能在各种介质中进行。琼脂凝胶具有分子筛的作用,筛孔很大,随着琼脂浓度不同,可允许分子量从十几万到几千万的大分子物质自由通过,大多数抗原,抗体的分子量都在二十万以下,它们在琼脂凝胶中几乎都是自由扩散。琼脂扩散法分为双向扩散和单向扩散,单向扩散在琼脂凝胶板上进行时显示环状沉淀,所以称“环状免疫单向扩散法”。 The free movement of matter forms a diffusion phenomenon that can occur in various media. Agar gel with the role of molecular sieve, a large sieve, with the agar concentration, allowing the molecular weight of tens of thousands to tens of millions of macromolecules freely through the majority of the antigen, the antibody molecular weight of 200,000 or less , They are almost free to spread in the agar gel. Agar diffusion method is divided into two-way diffusion and one-way diffusion, one-way diffusion in the agar gel plate showed when the annular precipitation, so called “annular immune one-way diffusion method.”