[Studies on the structure of thalamo-cortical projection neurons and interneurons in the Corpus geniculatum laterale pars dorsalis of albino rats after different histological treatments].

1. In the dorsal part of the lateral geniculate body of the albino rat (Wistar strain) the identification of relay neurons and interneurons has been carried out and the findings in Golgi and Nissl preparations were compared with those in the semithinn sections and in the electron microscopic preparations. 2. The effect of different histolical treatments (perfused by Karnovsky's fluid and embedded in micropal; immersed or perfused by Bouin's fluid, formalin or glutaraldehyde and embedded in celloidine or paraffin) in the structure of the relay neurons and the interneurons in combination with the Nissl method is described. 3. Following immersion the cytoplasm of the relay neurons is relatively broad and has a rough structure in the extreme case (glutaraldehyde) it is vacuolized due to hypoxie or anoxie. In these preparations we could not extimate dark neurons. 4. Following perfusion the cytoplasm of the relay neurons has a fine structure and is more narrow than following fixation by immersion. Furthermore the cell nucleus is enlarged. 5. The identification of interneurons is possible to a high degree of security only after fixation with one of the both aldehydes according to the well-known criteria. When Bouin's fluid is applied the chromatin particle at the nucleolus as one of the important discriminators is not represented. 6. In the single groups the relay neurons were characterized by quantitative parameters. As statistical method of calculation the paired comparison is used. The findings about the semithinn sections are regarded as the standard values because this material is expected to give the most reliable equivalent picture. 7. In 9 out of 12 cases the diameter of the cell soma is smaller and in 3 cases larger than the standard value. 3 values (perfused by Bouin's fluid and embedded in paraffin; immersed by formalin and embedded in celloidine; immersed by glutaraldehyde and embedded in celloidine) do not present remarkable deviation from the standard value. 8. Amongst the diameters of the nuclei only one value is larger than the standard value. 7 values do not significantly differ from the standard value, among them the values of meterial perfused by Bouin's fluid and embedded in paraffin and also immersed by formalin and embedded in celloidine. 9. All the quotientes from soma diameter and nucleus diameter are significantly different to the standard value. The difference between the values of immersion by Bouin's fluid and the standard value is the smallest one. 10. Although the values of soma diameter and nucleus diameter of the mateiral following perfusion by Bouin's fluid and embedding in paraffin as well as following immersion by formalin and embedding incelloidine are not significantly different to the standard value, we prefer immersion by formalin and embedding in celloidine because it is the most suitable method solving the special problems concerning the identification of relay neurons and interneurons in Nissl preparations and the metrical comparisons with findings in Golgi investigations.