It consists of an H-shaped piece of glass tubing, two legs of the H being longer than the other two. Glass test tubes or bottles are stoppered onto each of the longer limbs of the H and a suitable wire electrode passed through each stopper. The electrode is wrapped around the portion of the glass tubing projecting through the stopper. Each bottle and the lower halves of the longer limbs of the H are now filled with a N/1000 KC1 solution to which has been added enough sugar to make the solution of an appreciably greater density than the sol to be studied. With gold or other ordinary suspensoid sols 5510% sugar was found to be suitable. The sol to be studied is carefully pipetted onto the sugar-KC1 solution to form a supernatant layer in the upper portion of the H, filling it to a point above the crossbar. If a suitable e. m. f. is impressed on the two electrodes a movement of the two boundaries of the sol is easily noted. With 110 volts d. c. a movement of a quarter of an inch in fifteen minutes was obtained with a negative gold sol and a positive femc oxide sol. Upon reversal of the polarity, a reverse movement of equal magnitude was demonstrable. Several such devices can be connected in parallel for the comparison of various sols. Since the H-crossbar need not be fused together as shown in the illustration, but may be joined by means of a rubber tubing, such an apparatus can be assembled in a laboratory from ordinary T-tubes. Simple copper electrodes give very good qualitative results. It is true that a small amount of gas is liberated a t such electrodes, which tends to introduce an error in the movement of the boundaries of the sols. The magnitude of this error is not great. Silver-silver chloride electrodes can be prepared which do not liberate gas. For ordinary lecture demonstration the simple copper electrodes are to be preferred.
Thousands of Babies Treated with Calmette Tuberculosis Vaccine. Babies of four nationalities have been treated with the mast recently perfected tuberculosis vaccine of Prof. Albert Calmette of the Pasteur Institute. In an account t o the Academy of Ncdicinr o f hi.; latest results in rhc prolrrtim of newly horn children against tuberculosis. hr sratcc that 5000 babies h a w been suhlectcd t o thii treatment in France, 11. in Belgium, 3352 in Indo-China, and 218 in Senegal, West Africa. All of these children were born in tuberculosis-infected households and the vaccine was administered either through the mouth or by inoculation before they were ten days old. Up t o date less than 2 per cent of them, Prof. Calmette says, have succumbed to the diseasstriking reduction of the average mortality of 25 per cent for European children in tuberculosis homes. I n Paris the average is even higher, reaching 32.6 per cent. The vaccine apparently produces no harmful results while the immunity it confers lasts, according to Prof. Calmette, from 15 to 18 months. He recommends for best resl~ltsrevaccination a t the end of the fird and third years -Srience Servire
