Abstract
The colloid mill was found capable of disrupting bovine epididymal spermatozoa in such a way that even the very resistant sperm middle piece was opened. The homogenate thus produced was fractionated by both differential centri-fugation and isopyenic density gradient centrifugation. The latter method was found very useful in producing homogenous fractions of cell components including in order of increasing density: mitochondrial fragments, acrosomes, membranes, tail principal pieces, middle pieces, middle piece exteriors, contractile fibres and denuded heads. The mitochondrial particles consumed O2 while the cell membranes had hexokinase-like activity.