A detailed analysis of the effects of various fixatives on animal tissue with particular reference to muscle tissue.

Nine different fixatives (Carnoy's, Susa, Baker's formalin, 5% formalin, 10% formalin, 10% formol saline, Bouin, Zenker, and 2.5% gluta-aldehyde) were compared by two methods. Gelatin-albumin gels were used to study volume changes after fixation and after various stages of subsequent processing. The appearance and hardness of the gels were also noted. The fixatives either shrunk or swelled the gels, but dehydration and clearing shrunk the gels in all cases. Samples of muscle tissue from one location in beef longissimus dorsi muscle were also placed in the different fixatives and processed. Various features were noted for each fixative, including the ease with which the paraffin wax blocks were cut and the staining ability of the sections in Mallory's triple stain. The diameters of the muscle fibers were measured from transverse sections of these samples and compared with the mean diameter of muscle fibers in a frozen unfixed section of muscle tissue. It was found that the fixatives had the same shrinkage effects on both the gels and the muscle samples. Analysis of variance tests showed that the various fixatives caused different degrees of shrinkage. Statistical details are given for the amounts of shrinkage caused by each fixative. Both the general histological picture and the amount of shrinkage were considered when deciding the best fixative. Carnoy was found to be the best of the fixatives investigated.