Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 50. (Budapest 1958)

M. Nyírő, R.: The studying of Foraminifera in thin sections

Cummin g uses the so-called ,,

Marco Resin" material for the imbedding of the microfauna. His methods roughly corresponds with the one described by Hag n. Of the methods discussed above, the ,,polyester"-resin method of Hagn and C u nini i n g's treatment seem to be the most appropriate. Their advantage against the other ones is that there is no need for a heat treatment. In Hungary, E. Vadász, Gy. R a k u s z and L. M a j z o n worked on thin sectioning studies of Foraminifera. The microtechnique used by me is the following. For my studies, I used a synthetic imbedding material. The Czechoslovakian product „Spofacryl" proved to be the most suitable. The course of preparation is taxatively set out below : 1. The preparation of the imbedding material: we placed an amount (of two or three knife-points) of the powder on a sheet of glass, and added a polymerisator until it reached the suitable hardness, that is, plasticity. 2. The imbedding of the Foraminifera in the basic material : the specimens were placed orientated into the tooth cement paste under magnification ; even more than one specimen at a time, for the sake of obtaining as many cuts as possible. After the imbedding of the Foraminifera, we covered the synthetic mass with a cellophane sheet, placing a sheet of glass on it afterwards. Then, applyng a pression on the sheet of glass, we waited for one and a half or two hours for the hardening of the material. 3. Cutting : the hardened synthetic preparation was first cut on the imbedding side. Namely, the Foraminifera specimens are in the vicinity of the surface on the imbedding side. The covering layer is the thinnest in this place. We worked with the finestly grained cutting powder, on a glass sheet, controlling the cut surface at all times. Having reached the surface appropriate for study, we glued the preparation by Canada balsam onto an object slide, but carefully, since the synthetic imbedding material contracts on the action of heat. After gluing, we cut the other side of the- preparation. Cutting was first done on an iron sheet, then, having reached the suitable thinness, we continued it on a sheet of glass. The appropriately thin cut was covered by an object slide. In the course of cutting, we have established the following advantages of the use of this synthetic material : 1. For the preparation of the mass, room temperature is enough ; 2. The Foraminifere specimens can easily be imbedded into the paste under magnifi" cation ; 3. Due to the elasticity of the synthetic material, the danger of the cracking of the tests is considerably diminished ; 4. It is suitable also for making preparation series. Its disadvantage is that the polymerisator of Spofacryl binds rather quickly. This makes rather difficult the orientation of the specimens. For this cause, we used butylacetate instead of the original solvent. In this way, the binding effect of the paste slowed down, and orientation could be made conveniently. It appeared during sectioning that for the purposes of our studies especially the Fora minifera filled with minerals are the most suitable, since the walls of specimens of empty chambers cracked during cutting, impeding to obtain the necessary thinness. On the other band, the forms filled with pyrite are especially conforming for photographs, since, aside of the external, also the internal contours are well delineated. As mentioned above, the forms of thin calcareous tests or of empty chambers cause many difficulties. One has to be specially careful to cut these specimens, since the fine, thin separating walls will soon crack, but this also can be obviated by a careful cutting. Forms with such fine walls were not imbedded in Spofacryl but in ,,Superacryl", (also a Czechoslovakian product), the more so as the color of the wall did not contrast with the color of the first material. This method does not essentially differ from the first one, but the latter material has a strong rosy hue, thereby differing from the color of the imbedded specimen, so its study and photographing are also easier. I will introduce some thin section pictures in the followings. Photographing the cuts meant some serious difficulties, since we could not obtain a cutting thinness adequate for taking pictures. So the microphotographs are not always satisfactory. Recently, we make only surface cuts, since falling-on light is more appropriate.