552 



SCIENCE 



[N. S. Vol. LIV. No. 1405. 



conserved or broken; that is, worth in the sense 

 of highest attainment in functional grade and in 

 the approach to mentality. 



Chaeles Schuchert 



SPECIAL ARTICLES 



A SIMPLE MICRO-INJECTION APPARATUS MADE 



OF STEEL 



For injection and suction purposes in tlie 

 field of the compound microscope two very 

 good methods are in existence. One is 

 Barber's^ mercury pipette. This consists of 

 a glass tube completely filled with mercury. 

 One end is bent into several loops and sealed 

 at the tip. The other end is drawn out into 

 a capillary with a microscopic aperture at 

 its tip. The pipette is held in Barber's 

 pipette holder which is clamped to the stage 

 of the microscope. For injection and suction 

 purposes Barber depends on the expansion 

 and contraction of the mercury by varying 

 the temperature of the loops of the pipette. 

 This method gives excellent results but the 

 pipette is rather diificult to make, it is easily 

 broken and the driving force of the mercury 

 can not be instantly controlled. 



A more recent method is that of Taylor's,' 

 which also consists of a mercury -filled pipette, 

 but which depends upon a minute plunger 

 to regulate the pressure of the mercury. The 

 plunger method gives the operator a better 

 control of the pressure in the pipette but has 

 the disadvantage of possible leakage around 

 the plunger. This generally occurs after the 

 plunger has been used several times. A great 

 deal of time tends to be wasted in keeping 

 the apparatus in a working condition. 



The apparatus described here is very simple 

 to set up and, excepting for the few inches 

 of capillary pipette which can be inserted 

 into the apparatus within a few minutes, it is 

 permanently ready for use. The apparatus 



1 Barber, M. A., 1911, "A teehnic for the inocu- 

 lation of bacteria and other substances into the 

 cavity of the living cell," Jour. Inf. Bis., VIII., 

 348; 1914, "The pipette method," etc.. The Philip. 

 Jour. Sc, Sec. B, Trop. Med., IX., 307. 



2 Taylor, C. V., 1920, "An accurately control- 

 lable micropipette, " Science, N. S., LI., 617. 



depends upon leverage clamps to regulate 

 the mercury pressure which can be controlled 

 at any instant. Consisting entirely of steel 

 and heavy glass it is practically unbreakable, 

 a consideration of great importance for easy 

 manipulation. 



As in Barber's and Taylor's instruments, 

 mercury is used to procure the necessary pres- 

 sure. The apparatus consists of a thin-walled, 

 (.028 inch or less thick), straight, one half 

 inch, steel tube about six inches long (see 

 figure). Into one end of this is sealed an 



Fig. 1. 



accurately fitting steel or glass stopcock. The 

 other end leads into a small steel tube fine 

 enough to be flexible, viz., about 3/32 of an 

 inch in outside diameter. The small tube is 

 bent into a twisted S shape, so that, when 

 at rest, its tip lies on a pipette carrier on the 

 stage of the microscope. The tip of this thin 

 tube is furnished with a screw joint by means 

 of which it may be attached to a hollow steel 

 rod two inches long which carries the glass 

 micro-pipette. The outer end of the stopcock 

 is connected with a rubber tube about four 

 inches long. The steel tube is placed in a 

 special clamping device which is secured to 

 the table beside the microscope. This clamp- 

 ing device consists of three leverage clamps, 

 one of which presses on the steel tube in a 

 direction at right angles to that of the other 

 two. 



The apparatus is first filled with clean 

 mercury through a glass funnel inserted into 

 the rubber tube upon which the stopcock is 

 closed. The glass pipette is made according 

 to Barber's method^ and is sealed with wax 

 into the hollow steel rod. 



3 See footnote 2, also Chambers, E., 1918, ' ' The 

 microvivisection method," Biol. Bull., XXXIV., 

 121. 



