518 SUMMARY OF CUERENT RESEARCHES RELATING TO 



tion researches on acid, amphoteric, neutral, and alkaline media which 

 were made from sputum, potato, blood-serum, and from numerous human 

 and animal organs, that substrata with acid or amphoteric reaction are 

 far more favourable than those with neutral or alkaline reaction. The 

 best of all was a medium containing brain substance and having an acid 

 reaction. This was prepared in the following way : — Fresh brain was 

 passed through a mincing machine, two or three times, and the mass 

 mixed with an equal bulk of distilled water. This was then heated 

 slowly to boiling, being constantly stirred the while. After having 

 boiled for a quarter of an hour, the decoction was passed through a 

 strainer. The strained broth was then distributed into flasks, and steam- 

 sterilised for two hours. This stock broth was used to mix with serum 

 or agar. For the brain-serum medium equal parts of stock and serum 

 were used arjd then mixed with 3 per cent, glycerin. Slants in test- 

 tubes were made of this mixture in the usual way. The brain-agar 

 medium was made by mixing equal parts of a 2 • 5 per cent, solution of 

 agar and the stock- broth and then adding 3 per cent, glycerin. The 

 mixture was distributed into test-tubes, and the tubes steam-sterilised 

 for half an hour. 



During sterilisation brain-agar separates into two layers, the upper 

 one being agar, the lower brain substance. It is, therefore, necessary to 

 shake the tubes well and make them set as soon as possible to prevent 

 the brain substance sedimenting. Any kind of brain may be used ; the 

 serum recommended is horse-serum. The growth on these brain media 

 is very satisfactory, as regards both amount and rapidity of development. 

 Brain may also be used after the manner of potato. For these cultures 

 a brain is set by steaming it for 1-1^ hours. It is then cut up into 

 slices which are placed in test-tubes or capsules. In the test-tubes 

 about 10 drops of 3 per cent, glycerin are placed ; in the plate-cultures 

 15-20 drops. The tubes and capsules are then steam-sterilised twice for 

 half an hour. The slices should not be too thin. 



Cultivating and Staining the Nodule Organism of the Legu- 

 minosae.*— Mr. R. Greig Smith has obtained excellent growths of the 

 nodule organism with a faintly acid medium containing 1 per cent, 

 pepton, 5 per cent, glucose, and 0'5 per cent, potassium chloride. Air- 

 dried films, fixed by floating on 5-10 per cent, formalin, were stained 

 with carbol-violet, washed, air-dried, and mounted in balsam. When 

 prepared in this way, the organisms appeared as more or less oval 

 capsulated yeasts with vacuoles and terminal buds. The diversity of 

 shape depends on the thickness of the capsule, the nature of which 

 is dependent on the cultivation medium. Glucose tends to produce thin 

 delicate capsules, while with sucrose they are tough. By using an 

 undiluted young pepton-glucose culture, fixing in formalin, and stain- 

 ing with Coerner-Fischer solution, the author succeeded in staining the 

 flagellum. This flagellum is thin, single, terminal, about 2 /x long, 

 with a tuft at the distal end. 



Influence of Metals on Broth Cultures of Bacteria, t — Heir B. 

 Isachenko states that experiments* with Bacillus spermophilinus showed 



* Ceutralbl. Bakt u. Par., 2 t0 Abt., vi. (1900) pp. 371-2. 

 t Selsk. Khoz. Lyesov., clxsxix. (1898) pp. 35-42. 



