A Centrifuge-MicroscopeSource: The Scientific Monthly, Vol. 35, No. 1 (Jul., 1932), pp. 95-96Published by: American Association for the Advancement of ScienceStable URL: http://www.jstor.org/stable/15484 .

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THE PROGRESS OF SCIENCE 95

A CENTRIFUGE-MICROSCOPE

... .. ...2

4~~~~~~~~~~4

THE INEWN CEA NTRIFI(GE M-ICROSCOPE TiIs DEXICIE PERMITS THE OBSER\ATION OF TIl F. CHANGES TA\KING PLACE \X ILImIN (ELLS AS THEY A1RE S1UBJEC(TED TO (AENTRIFUGAL FORCE. THE

(CLL IS PLAC('El) Al' ONE ',.NI) OF T1IE HOLLOW BIAR

AND IS AWHIIRLED) \BOI-T ON THE TI-RNrTABLE. BY MIEAN'S OF A SERIES 0' IF,NSES NI) -MIRRORS W\ITIIN TILE BAR TILE IMAGE OF TIlE CELL IS CARRIED TO TE, (CENTER OF THIE BAR SO THAT IT IS WNVITHIN TIE RANGE OF THE SUSPENDED EYE- PIECE. TIIE SMALL MERCURY LIGhIT, SEEN ABOVE THE END 0OF TIIE BAR, FLASTIES ON THE REY'OLYING CELL AS IT PASSES BENEATII, CREAT- ING A SERIES OF I-MAGES WHIIICI AFFORD TIIE OBSERVER A CONTINUOUS AND STEADY PICTURE OF TILE2, CELL. TIIE PRINCIPLE IS SIMILAR TO

TIIAT OF A MOTION PICTURE IPROJECTOR.

AxN advance in biological kHowledge is expected to restult fromii the use of a new type of miiciroseope which hlas beeni evolved by Dr. E. -Newton Harvey, of Princetoii University, ancd Alfred L. Looiniis. By means of this instrum:lenit observationis can be Ii1ade nponi the ellanges taking place within cells as tlhey- are subjected to celltrifnioal force. Pre- liminary caleulations already maide with the lhelp of the new imieroscope indicate that existing ideas of some of the prop- erties of matter \ithlin the cells will have to be revised.

Hitlherto scientists havTe been lianidi- capped in their stndy of cells by their

inability to -witness aind mleasture the v'ariotIs steps in the dlefornmationi of cells anid in the movement of particles withlini tlheimi wheni the cells are wvlhirled rapidly about. Knowledge of -what tranispires when cells are subjected to centrifugal force has beenl based oIn deductions formiied b- examination of the cells be- fore and after they lhave beemi in miiotioni.

Although the cell is bein - whirled about at a rate of 10,000 revolutions a inunte, the new imiieroseope presents time

observer wi-itlh a, clear, steady picture of it throtuo,hout the procless. The priin- ciple is somewhat similar to that of a miiotioni picture projector, with the whirl- ino- cell taking the place of the filmii andcl the eve of the observer the screeni. The mechlaniismii transmits to the eve a series of imlaoges w itlh such reocularity and rapidity that tlhey blenid imito a steady, continiuouis picture.

TIn the newv centrifuoce-microscope a disc or turintable siihnilar in size aii(1 op)er.ation to that in a phonog raph is rotated at hiioglh speed by ain electric iimotor. Mounted oni the disc anid extencd-

. ......

AN AMOEBA IN ROTATION Aminoeba du.bia INJECTED W.ITH OIL By DR. D. A. \.RSLAND, PHOTOGRAPHED THROUGH THE CEN- TRIFUTGE-MTICROSCOPE WHILE REVOLVING 10,000 REVOLUTIONS PER MIINUTE. ExposUTRE 10 SEC-

ONDS.

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96 THE SCIENTIFIC MONTHLY

Ir r,..,,,.'el's iNA':;'dn'l~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. .. .....

.hILE REVOLVING 10,000 REVOLUTIONS PER MINUTE FOR ONE MINUTE (CENTE) AD FOR. . FIVE MIN TESU (RIGHT). NOTE....... . TIlE BLACK M S OF OL ....... .O . T . O C N iFA......... F R E

E"'0.>.'.'<".m'.;t'.? ......... .' ......... :.: .' "">^.' ' :' . :.]~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..... .. ..... :4:':

' ,~~~~~~~~~~~~~~~~~~~~~~~~~~~~.::. ::.: _, . !... ..... .. .... .... .. . . ..... ': _;_BS

I * _> C .............. :. .::. ::::ums: 'M _e3,,,'>,8.e'.,^i ................... .'3 ............... .5!4.::: ..... : ': . ,2_~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. . . .... . . l S L_g_ ' _~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.... .. . | , . _ l .......................... | . | 11-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. . . ...

PARAMECIUM AT REST AND IN ROTATION

PARAMIECIUMI FILLED WVITH FAT GLOBULES PHOTOGRAPHED W\ITIH CENTRIFUGE AT REST (LEIPT) AND

WHTILE REVOLVING lQ,OOO REVsOLUTIONS PER MIINIUTE FPOR ONTE -MINUTE (CENTER) AND FOR FIVE

MIINUTTES (RIGH-T). NOTE TIIE BLACK AIASS OFP OIL ABOI,T TO PULL OFF U-NDER CENTRIFUGAI. FORCE.

ing along its diameter is a hollow alumi- nuni bar one half inch thiek. In this narrow bar has been built the lower lens system of a microscope. This is con- tained beneath an aperture at one end of the bar and is near, consequently, the outer edge of the disc. Above this aper- ture is placed the slide holding the cell which is to be observed. By a proper arrangement of mirrors, the image is carried to the center of the bar and is reflected upward through a second aper- ture to the upper lenses and the eyepiece of the microscope. This working end of the microscope is supported directly over the center of the disc and is sta- tionary.

This arrangement provides a means of constantly observing the cell when it is in motion, but the image, if it can be seen at all at rapid speed, is nothing but a blur. The problem of obtaining a clear imag,e was solved by the adapta- tion of the principle of the motion pic- ture projector. The solution consisted in catching a glimpse of the cell for a fraction of a second during its whirl and in making possible the repetition of that glimpse at frequent and regular inter- vals. Thus through the projection of a series of inmages, a continuous picture results.

This series of images is produeed by

flashing a. light at regular intervals above the whirling disc. The light is so regulated that its flashes coincide with the passage of the cell beneath it. The flash lasts for about one one-millionth of a second. The speed of rotation of the disc controls the frequency of the flash. Standing away from the whirling disc and looking upon it, the observer is sub- ject to an optical illusion. The disc does not appear to be moving at all and the bar seems to be stationary beneath the light. The flash is produced by a small mercury light, the duration and inter- mittency of which is controlled by the discharge of electricity through the mer- cury vapor.

The present microscope is capable of making 10,000 revolutions a nlinute. Its speed is limited by the resistance of the air to the hollow aluminum bar. In a new model the bar has been stream-lined to cut down this resistance and in cross- section it will have lines not unlike those of a racing automobile.

It i,s expected that this model will develop speeds of from 12,000 to 14,000 revolutions a minute. A speed of 12,000 revolutions will subject the cell to a centrifugal force 17,000 times greater than gravity. This may be compared to a pull of eight and one half tons upon an object which weighs one pound.

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