Stereoscopic Studies of Cells and Viruses in the Electron Microscope

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Abstract
With its great resolving power and enormous depth of field the electron microscope is ideal for stereoscopic work at high magnifications. However, most biological specimens are not suitable for stereoscopic study because they become flat when they are dried before insertion in the high vacuum of the instrument. When the stresses due to surface tension have been eliminated by using the critical point method of drying (Anderson, T. F., Trans. N. Y. Acad. Sci., Ser. II 13: 130-134. 1951), biological specimens retain their shapes. For example, stereoscopic electron micrographs of ghosts of human red cells and spirilla show that they retain their shapes after having been prepared by this method. When dried in this way the "heads" of the phages T2, T4, and T6 appear 6-sided as though they had the shapes of short hexagonal prisms capped by 2-hexagonal pyramids, to one of which the "tail" or "stalk" is attached. The head of the unrelated phage T5 has a prismatic appearance, too, and after inactivation by gentle heating in the absence of Ca ion, the internal structure escapes to leave behind the hollow shell of the head with the tail still attached. It is also seen that bacteriophages T2, T4, and T6 adsorb on their host cells (Escherichia coli B) by their "tails.

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