MICROMANIPULATION 



154 



MICROSOMES 



manipulator so that the tip extends 

 over the microscope stage into a moist 

 chamber. The bent-up tip is adjusted 

 with the screws of the instrument until 

 the tip lies in a hanging drop of fluid 

 suspended from a glass cover-slip serv- 

 ing as the roof of the moist chamber 

 and in the field of the microscope. 



Injections are performed by breaking 

 the tip of a mieropipette against the 

 undersurface of the coverslip while the 

 tip is in view under the microscope. 

 Capillarity draws fluid into the shaft 

 of the pipette when the open tip is in- 

 serted into a hanging drop of fluid, be 

 it oil or any given solution. For micro- 

 injection, the pipette holder, mounted 

 on the instrument, is attached to a 

 looped, capillary brass tube of which 

 the other end is attached to the nozzle 

 of a syringe. Before mounting the 

 mieropipette, the syringe is filled with 

 water and, by means of the plunger, the 

 water is driven into the brass tubing 

 and the pipette holder after which the 

 mieropipette is inserted. Thus, we 

 have a water-filled system extending 

 from the syringe to the base of the 

 mieropipette which is filled with air. 

 Micro-amqunts of any given solution 

 are then drawn into or ejected from the 

 * tip of the mieropipette by a delicate 



handling of the plunger of the syringe. 



The instruments are generally supplied 

 in pairs, one part carrying a micro- 

 needle for holding the tissue to be 

 injected, the other carrying the miero- 

 pipette. For microdissection, the in- 

 strument carries two needles, each of 

 which can be operated independently. 



Wilhelm PfefTer, to whom we owe the 

 term "plasma membrane" for the limit- 

 ing boundary of protoplasm, stated, in 

 one of his papers in 1887, that an instru- 

 ment with which one could operate 

 delicate needles and pipettes in the 

 field of a compound microscope would 

 go far toward the elucidation of the 

 nature of living cells. Pfeffer's dream 

 has been realized in the development of 

 the special field of science called today 

 Micromanipulation or Micrurgy. 



Of general interest, and also for many 

 details not described elsewhere, are the 

 following: Barber, M. A., Philippine J. 

 Science, B, 1914, 9, 307; Chambers, R., 

 Anat. Rec, 1922, 24, 1; P^terfi, T., in 

 methodik der wissensch. Biologie, 1928, 

 1 (4), 5; and Schonten, S. L., Zeit. f. 

 wiss. Mikr., 1934, 51, 421. An excellent 

 book which covers a broad range of the 

 field of Micrurgy is that of J. A. Rey- 

 niers Micrurgical and Germ-Free Tech- 

 niques, C. C. Thomas, 1943. 

 Micrometry is the measurement of an object 

 observed microscopically. This can be 



done either by using an ocular microm- 

 eter in which there are lines which can 

 be accurately moved the length of the 

 structure to be measured or by inserting 

 a ruled disc in an ordinary ocular with 

 which it can be compared. Both must 

 be standardized in relation to a microm- 

 eter slide generally ruled with lines 10^ 

 apart. 



Micromicron (mm) = 1/1, 000 ,000th part of a 

 micron = 1/1, 000 ,000 ,000th part of a 

 mm.„= 10-9 mm. = 0.000,001 micron = 

 IQ-^A. Unfortunately often used syn- 

 onymously with ^millimicron (m/x) = 

 0.001 micron = lOA. 



Micron (Gr. Mikros, small) expressed by 

 Gr. letter n = approximately 1/25,000 

 inch = 1/1000 part of a mm. = 0.001 

 mm. = 10-3 mm. = 10,000 A (see 

 Millimicron and Micromicron). 



Microphotometer, see Photoelectric. 



Microradiographic examination. This con- 

 sists of magnification of a Roentgen ray 

 image after it has been registered pho- 

 tographically. The essential point is 

 to use film of very fine grain emulsions. 

 Thus the Gevaert Lipmann emulsion 

 permits enlargement 300 times without 

 much loss of detail. In some cases it 

 is helpful before microradiographic 

 examination to increase the absorption 

 of Roentgen rays by "absorption stain- 

 ing" through adding radio-opaque mate- 

 rials such as barium sulpnate and thoro- 

 trast. The application of this technique 

 in the study of biologic materials 

 is described and illustrated by Clark, 

 G. L. and Bick, E. J., in Glasser's Medi- 

 cal Physics, 730-733. 



Microrespirometer to indicate production of 

 carbon dioxide by bacteriophages, 

 viruses and bacteria (Bronfenbrenner, 

 J., Proc. Soc. Exp. Biol. & Med., 1924, 

 22, 81-82. 



Microscope. The ordinary microscope usu- 

 ally has darkfield equipment and needs 

 no description. A special illuminator 

 to throw light down on the object has 

 been devised (Preston, J. M., J. Roy. 

 Micr. Soc, 1931, 51, 115-118). Centri- 

 fuge, Fluorescence, Electron, Polarizing, 

 Ultraviolet, Metallurgical, and Darli- 

 field Microscopes. 



Microsomes (G. mikros, small, soma, body). 

 Term introduced by Hanstein in 1880 

 originally to indicate tiny granules — as 

 compared with ground substance. 

 Claude, A. Biological Symposia, 1943, 

 10, 111-129 estimates their size to be 

 50-300 m/x and therefore beyond limits 

 of ordinary microscopic visibility. 

 These microsomes of Claude are ob- 

 viously not the ones which Hanstein 

 had in mind. According to Claude 

 they are essentially ribose nucleopro- 



