128 



A. KLEINSCHMIDT 



Fig. I. Microdroplet from Paris PL 1/49 virus strain. 



greatly simplified and pipettes of a perfectly cylindrical 

 shape can be made. In the case of say 30 microns, a 

 quantity of about 2 10" ml can be separated 

 and placed individually on the film. 



The micro-pipettes are operated with mercury 

 pistons. This requires a pressure of several atmos- 

 pheres. For this purpose a special small hydraulic 

 apparatus has been constructed. This hydraulic 

 method of operating a micro-pipette is practically 

 free of inertia so that in separating the micro-volume 

 to be measured, the length of the column can be set 

 at any desired position and read by means of the 

 ocular micrometer. There is an air cushion between 

 the liquid and the mercury. We de not count on a 

 loss in material because these micro-pipettes can 

 easily be siliconized. 



To preserve these minute quantitities of liquid, 

 micro-manipulation takes place in a moist chamber 

 (4). The objective is protruding into the chamber. 

 The specimen holder is placed on the base of the 

 chamber. The objective lense is furnished with an 

 anti-dim covering layer. The chamber can be kept 

 at any useful temperature. The formvar covered grid 

 is gently pressed against the surface of a small piece 

 of moderately dried agar-plate. When the droplets 

 are placed on the film, their moisture is absorbed 

 by the agar-plate and the particles settle on the film. 



All the manipulative tools are mounted on the 

 Zeiss micromanipulator. 



Fig. 1 shows a droplet taken from the Paris PL 

 1 49 virus strain. The number of counted particles 

 in these pictures are 440. All counts fell between 

 417 and 490, and we could determine the absolute 

 particle number. 



As to the pipette calibrations, two types of meas- 

 uring were tried. By means of x-ray microradio- 

 graphy silhouettes of mercury-filled pipettes were 

 obtained. For very thin pipettes, however, satis- 

 factory results have not yet been attained. So we 

 made use of a thought of de Fonbrune (2) and cali- 

 brated micro-pipettes by pressing micro-droplets of 

 water into paraffin oil, taking water columns which 

 were identical with those applied in the original 

 experiment. This type of calibration gave a constant 

 error of 4-10 %, depending on the diameter of the 

 pipette. 



References 



1. Backus, R. C. and Williams, R. C. /. Appl. Pins. 21, 11 



(1950). 



2. DE Fonbrune, J., Technique de Micromanipulation. Mas- 



son et C'^ Paris, 1949. 



3. RiEDEL, and Ruska, E., KoUoid-Z. 96, 86 (1943). 



4. Sugar, I., Z. wiss. Mikroskop. (in press). 



tjber die quantitative Spreitung von Zellen. 

 Eine Untersuchung (dlinnster Filme mit dem Elektronenmikroskop 



A. KLEINSCHMIDT 



Hygiene-Institut, Frankfurt am Main 



Neben qualitativen Spreitungsversuchen an Zellen, 

 wie sie zur elektronenmikroskopischen Darstellung 

 cytologischer Objekte seit Hartman u. a. (8), von 

 Senseney u. a. (16), Kleinschmidt (12, 13) und 

 Herzberg u. a. (9) angewendet wurden, ist eine quan- 

 titative Analyse der Filme mit mikroskopischen 

 Teilchen auf einer Wasseroberflache, dem Substrat, 

 angezeigt. Damit erhalt man einen besseren Einblick 

 in den komplexen Vorgang. Methodisch setzt sich 

 die Untersuchung aus drei Teilen zusammen: 1. Die 



Filmerzeugung und Filmeigenschaften; 2. die Uber- 

 tragung auf feste Triiger und 3. die licht- und elek- 

 tronenmikroskopische Darstellung. 



1 . Jeder unlosliche Film auf einer Wasserober- 

 flache erzeugt in komprimiertem Zustand einen 

 Schub, der in dyn cm gemessen werden kann. Wir 

 benutzen einen Langmuir-Trog zur Filmerzeugung 

 und messen den Schub mit einer Oberflachenwaage 

 vom vertikalen Typ (4, 7, 18). Man erhalt damit 

 von aufgebrachten Proteinfilmen, wie von Kinder- 



