ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 117 



coloured. While the alkaline carminutes tend to remain in the cells, 

 the acid-carmin do not tarry long, and are totally eliminated by the 

 Malpighian tubes. 



Method for Quick Detection of Spirochseta pallida.* — W. H. S. 

 Stalkartt recommends the following procedure : — 1. Fix in 1 p.c. glacial 

 acetic acid and 8 p.c. formahn ; rough-dry the slide. 2. Wash in alcohol 

 and flame off. 3. Gently heat in 5 p.c. solution of tannic acid. 4. Wash 

 in water and stain with slightly warmed silver nitrate solution. (To a 

 5 p.c. solution of silver nitrate add ammonia solution until the precipitate 

 first formed is just dissolved ; add a few more drops of silver nitrate 

 solution until the precipitate just reappears.) 5. Wash in distilled water 

 and dry : the films must not be mounted in balsam. 



(6) Miscellaneous. 



Method of Cleansing Living Mussels from Ingested Sewage 

 Bacteria.f — J. Johnston, working in connexion with the Lancashire Sea 

 Fisheries Laboratory and at the Sea-fish Hatchery at Piel, near Barrow, 

 has conducted an exhaustive investigation in relation to the purification 

 of contaminated Molusca, and has arrived at certain important conclu- 

 sions. It was found that the process of self-cleansing of sewage-polluted 

 shell-fish by placing them for some days in clean sea-water depended on 

 (a) the ingested bacteria being washed out from the mantle cavity and 

 internal cavities by virtue of the continuous stream of water circulating 

 through these passages ; and {h) on the fact that the bacteria rapidly die 

 out of a medium which is unfavourable for their development. The 

 optimum temperature of truly intestinal bacteria is about 37° C, i.e. the 

 temperature of the interior of the bodies of mammals, whilst the tempera- 

 ture of sea-water and the interior of marine molluscs is about from 

 3°C. to 15° C, and it has been ascertained that fajcal micro-organisms 

 disappear very rapidly when introduced into sea-water — the destruction 

 of some 90 p.c. of the organisms being effected in the first forty-eight 

 hours. In one case the average number of sewage bacteria estimated 

 was 7,100 per shell-fish. The mussels were put into glass aquarium 

 tanks of about 10 litres capacity, and sea-water was run through the 

 tanks at the rate of about one litre per five minutes. Samples of the 

 mussels were taken at intervals of one, two and four days, and it was 

 found that on the second day the average number of bacteria per 

 mussel had fallen to 116 — i.e. a reduction of 98*5 p.c. 



The same result can be brought about by the addition of chlorine, 

 a concentration of chlorine in sea-water of 5 parts per million being 

 sufficient to sterilize the water, while it does not interfere with the 

 ordinary functioning of the shell-fish. The action of the chlorine is 

 twofold : in the first place, it renders the polluted sea-water practically 

 free from sewage bacteria, and then this sterile water washes out the 



* Brit. Med. Jouni. 1915, ii., pp. 895-6. 



t Proc. and Trans., Livi rwol Biol. Soc, xxix. (1914-15), pp. 119-70 (with 

 plates, charts and text figs.). 



