Recapitulation is a bold and influential idea that is particularly associated with Ernst Haeckel though many other biologists also supported it in the nineteenth and early twentieth centuries. According to the theory of recapitulation, the stages of an organism’s development correspond to the species’ phylogenetic history- in a phrase, “ontogeny recapitulates phylogeny.” Each stage in development corresponds to (that is, [...]
The disinfection process does not take place at once but is a gradual operation in which the number of organisms killed in unit time is greater at the beginning and becomes less and less as the exposure period is increased. If the numbers of survivors in unit volume are plotted against time, the points fall on smooth curves. If the [...]
The method generally employed for the evaluation of germicides is to rate them according to their phenol coefficients. In addition to this, a number of newer methods have been proposed, which are designed to measure the toxicity of germicides for tissue as well as for the test bacteria. 1. Phenol-Coefficient Method: The phenol-coefficient test was first proposed by Rideal and [...]