Aceto-Orcein and Feulgen Stains for Anatomy and Cytology of Trematodes

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Abstract
Dicrocoelium dendriticum and Fasciola hepatica were killed in the extended condition without anesthetization by dropping them into 40% acetic acid or into aceto-orcein. By using aceto-orcein (La Cour, 1941), killing, fixing and staining were accomplished simultaneously: staining time 24 hr or more. Whole mounts were made by dehydrating, clearing and mounting in Canada balsam, or testes or the upper part of the uterus could be removed for squash preparations after as long as 2 mo in the fixing and staining fluid. For Feulgen staining, living specimens were placed in 40% acetic acid for 10—15 min and then transferred to either Gilson's fluid, for sections, or to acetic-ethanol (1:3) for squashes. Hydrolysis was either by 10% perchloric acid at 25°C for 12 hr or in 12V HCl at 60° for 10 min. The time for Feulgen staining (De Tomasi, 1936) was 1.5-4.0 hr. Squashes were made from testes and uterus in the same manner as after aceto-orcein or sections obtained after embedding in paraffin.