250 SUMMARY OF CURRENT RESEARCHES RELATING TO 



meningococcus, while if the dosage be increased, say to 1 * 5 p.c, NaCI is 

 relatively harmless. If, however, CaClg be added, the action of NaCI 

 is antagonized, and if KCl also be added there is a copious growth of 

 meningococcus. Distilled water failed to kill the coccus after twenty- 

 four hours. From the foregoing results it might be inferred that 

 0*85 p.c. NaCI might be a substitute for Flexner's serum. 



Protozoa in Relation to Soil Bacteria.* — T. Goodey records a 

 continuation and an extension of previous work on this subject.f The 

 recent conclusions are — 1. Protozoa, especially amceb^ of the Umax 

 group and other large forms, can lead an active existence and multiply 

 in soil and exert a depressing effect on bacterial numbers. 2. It is 

 probable that for a given soil a certain point must be reached in 

 protozoal numbers before the depression in bacterial numbers is caused. 

 In the soil investigated this number appears to be approximately 

 30,000 Ammha Umax per gramme. 3. It appears to be necessary to add 

 the protozoa to a treated soil in a small quantity of untreated soil to 

 ensure their having a suitable medium in which to grow and multiply. 

 Under these conditions it is shown that they can increase in numbers 

 and depress the numbers of bacteria. 4. It does not appear to be 

 possible to carry out mass inoculations of protozoa into treated soil in 

 such a way that they come into action and limit bacterial activity, and 

 the explanation advanced to account for this failure is that the treated 

 soil alone affords an unsuitable medium for the active trophic existencer 

 of protozoa. 



Bacterium campestre.J — Ethel M. Doidge contributes a paper on 

 the occurrence in South Africa of Bacterium campestre, the organism 

 which causes the black rot disease of the cabbage and other cruciferous 

 crops. This organism had formerly been recorded only from Europe, 

 America, and New Zealand, but the author's investigations showed that 

 the disease caused by it was quite common in the neighbourhood of 

 Pretoria. The most interesting point about the communication is- 

 that it seems clear that the organism was introduced into South Africa 

 on cabbage-seed which came from England. From cabbage-seed im- 

 ported by the nurseryman to whose premises the diseased plants first 

 observed by Miss Doidge were traced, the organism was isolated, and its 

 virulence proved by the successful artificial inoculation of two healthy 

 cabbage-plants. It was suggested nearly twenty years ago by Stewart 

 in America that this disease was probably disseminated by seedsmen,, 

 but actual proof was then wanting. Soon after this the organism was 

 isolated by Harding from the surface of cabbage-seed produced by 

 diseased plants in Long Island ; and now Miss Doidge has shown that by 

 such means the disease may be carried from one continent to another^ 

 Soaking suspected seed for fifteen minutes in 1-240 formahn or in 

 1-1000 mercuric chloride is recommended as a suitable method of treat- 

 ment. 



* Proc. Roy. Soc, Series B., Ixxxix. (1916) pp. 297-314. 

 t See this Journal, 1915, p. 397. 



X South African Journ. Sci., xii. (1916) No. 10. See also Nature, Feb. 22, 1917,. 

 p. 500. 



