252 



NATURE 



[February 23, 1922 



The Standardisation of Radium Ampoules for Therapeutic Use. 



A N apparatus for the routine standardisation of 

 •^~*- ampoules containing radium compounds and 

 emanation by the 7-ray ionisation method was in- 

 stalled recently at the Institut Curie. It consists, as 



H ABU ''■'^'^^^^^HII^^H 



Fig. !.• — Apparatus for the standardisation of radium ampoules (one-tenth full size) 



shown in Figs, i and 2, of a screened ionisation 

 chamber A connected directly to a gold-leaf electro- 

 scope B. The ampoule to be tested is placed in an 

 aluminium tray on the support C, which can be 

 slid along a graduated rule D. The intensity of 

 the ionisation current is deduced 

 from the rate of fall of the gold-leaf. 



A novel feature of the apparatus 

 is the method of charging the 

 electroscope by means of a variable 

 multicellular condenser E, which 

 obviates the need for a high-voltage 

 battery. 



The fixed plates of the condenser 

 are connected to the frame, whilst 

 the movable plates are mounted on 

 a spindle actuated by an ebonite 

 knob. When the condenser is 

 in the position of maximum 

 capacity a projecting finger F 

 brings the movable plates 

 momentarily into contact with the stem H, to which 

 is connected a low-voltage batterv (10-20 volts). On 

 turning the movable plates through 180° the same 

 finger comes into contact with another stem J con- 

 nected to the electroscope ; at this instant the capacity 



of the condenser is at its minimum and the potential 

 prof>ortionately increased (about thirty times). 



The gold-leaf is observed by means of a micro- 

 scope K the eyepiece of which is fitted with an 

 angular scale ; a small mirror L serves 

 to illuminate the field of the micro- 

 scope. The ionisation chamber con- 

 sists of a cylindrical brass box con- 

 taining a thin aluminium disc M, 

 which is connected to the electro- 

 scope through the amber-insulated 

 rod N. The end of the box f;u:ing 

 the ampoule is closed by a screen 

 consisting of two lead plates each 

 5 mm. thick. 



A modification of the apparatus is 

 used for measuring the radio-activity 

 of ores, earths, etc. The electro- 

 scope, the charging condenser, and 

 the substance to be tested occupy 

 separate compartments of a cylin- 

 drical brass box. The radio-active 

 substance is placed on a tray 

 immediately underneath a rounded 

 stem, the upper end of which forms the pillar of the 

 electroscope. The latter is charged by means of a 

 variable condenser identical with the one previously 

 described, but it can, if desired, be charged indepen- 

 dently or connected to a separate ionisation chamber. 



Fig. 2. — Sectional view. 



The electroscope is "earthed" by turning a milled 

 head. 



Both instruments were designed by M. Holweck, 

 of the Institut Curie, in collaboration with the manu- 

 facturer, M. Beaudouin, Paris. 



Life-cycles of Bacteria. 



T N a preliminary communication published in 1916 

 ■*■ Dr. Lohnis expressed the view that all bacteria 

 pass through a definite life-cycle, and the present 

 publication ' is an extensive review of the literature in 

 support of that contention. The volume also Includes 

 a chapter on methods, an extensive bibliography, and 

 more than 350 microphotographs of the forms ob- 

 served. 



Briefly, the life-cycle Is as follows : — Under cer- 

 tain conditions the cells come together and fuse, 

 forming an amorphous mass — the symplastic stage — 

 in which the protoplasm undergoes a thorough mix- 

 ing. The symplastic stage Is formed not only In 

 cultures In artificial media, but, in the case of the 



1 Part I, Review of the Literature (1838-1918). By Dr. F. Lohnis. 

 National Academy of Sciences, Washington, vol. 16, second Memoir. Pp. 

 252+41 plates. 



NO. 2730, VOL. 109] 



pathogenic organisms. In the body of the host as well. 

 It forms the connecting link between the various sub- 

 cycles of which the life-cycle of the organism may 

 be composed. All kinds of vegetative cells, as well 

 as all the varieties of reproductive organs described 

 by the author, can give rise to the symplastic stage. 

 From the symplasm the so-called regenerative units 

 always arise, and these either grow Into new cells 

 or several of them unite to form new cells 

 directly. 



Six distinct types of reproductive organs have been 

 described by the author. These are : — (i) Gonldia, 

 two to four or more In each cell. Thev are generally 

 motile and slightly more resistant than vegetative 

 cells. Many are filter passers. They grow into 

 vegetative cells. (2) Regenerative bodies, distinct 

 from regenerative urilts. They are spherical, oval. 



