A critical comparison of the freehand razor-blade dissection method according to Wilson with an in situ sectioning...

Two methods of dissecting rat fetuses are compared: the generally well-known freehand razor-blade dissection method according to Wilson and an in situ sectioning method (ISM). For this purpose the substance EGYT 1978 was used, which induces--inter alia--cardiovascular anomalies. Thirty-nine gravid rats were given either the test drug (EGYT 1978, 400 mg/kg body weight) or the vehicle orally from the 6th to the 15th day of gestation. The fetuses were assigned randomly to either dissection group. Both methods of examination revealed approximately the same number of anomalies per organ system. A comparison of the types of anomaly found showed, however, relevant differences in the nature of the changes revealed by the two methods. The in situ sectioning method was clearly superior to the freehand razor-blade dissection method for the detection of discrete anomalies of the cardiovascular system. We therefore recommend the in situ sectioning method as the method of choice for examining small fetuses from teratological experiments.