502 SUMMARY OF CURRENT RESEARCHES RELATING TO 



vein, say in the proportion of 1 of trypsin to 4 of blood. Sub- 

 sequently this unelotted blood should be planted into broth-tubes for 

 incubation, or where this cannot be done, the blood may be incubated 

 without dilution, and the growth of organisms sought for in the plasma. 



Cultivation of Tissues from Amphibians.* — J. C. Johnson chiefly 

 used Diemyctylus torosus in his experiments, and thus summarizes his 

 results : — 1. Nerve-growth observations indicate an out-pulling of 

 nerve-fibre, rather than an outpushing. Progress outward is by means 

 of pseudopod-like processes. 2. GiU-like processes appear on tissues 

 from the head region of the body. 3. Flat drops of serum produced 

 better results than deep rounded drops, causing tissue to be up against 

 the solid cover-slip ; they afford also better conditions for study with an 

 oil-immersion lens. 4. A common Stender dish with moist cotton in 

 the bottom offers a good way for cultivating a large quantity of tissue. 

 5. At other points than the tips of outgrowths, bacterial infection at first 

 increases activity. G. Diemyctylous tissues thrive best when washed in 

 Ringer's solution, and transferred about every two days to a fresh 

 medium. 7. Increased toxin condition of serum and tissue causes 

 decreased heart activity ; the heart-beat increases in proportion to the 

 increase of temperature. 8. Gill-like outgrowths can be moved in any 

 desired direction by changing the position of a hot pin applied to the 

 surface of the cover-slip. 9. Connective tissue was kept in a healthy 

 growing condition for forty-one days, when it was accidentally killed. 



(2) Pi'eparingr Objects. 



Method for Preparing the Scales of Eels and Other Pishes for 

 Mounting. — A. Gardolfi Hornyold, Aquario Yasio de Gama, Lisbon, 

 says it is by no means easy to prepare perfectly cleaned scales for 

 microscopic examination, as they are easily damaged. Having during 

 the last year worked on the determination of the age of the eel by the 

 scales, it was found necessary to find a method enabling him to prepare 

 a large number of scales rapidly and without damage. The scales are 

 obtained by scraping the skin with a sharp scalpel, and are then placed 

 in weak alcohol, or simply in water, to macerate for twenty-four to 

 forty-eight hours. The scales are then centrifugalized and the water or 

 alcohol poured off and fresh water is substituted ; after repeating this 

 operation three or four times one obtains perfectly cleaned scales, which 

 can be selected with the dissecting Microscope. A simple hand-driven 

 centrifuge as used by doctors for urinary examination, etc., is suitable 

 for this work ; though of course an electrically driven centrifuge is 

 more convenient. The author found no difficulty in preparing the 

 scales of a dozen eels in a morning by this method. This method gives 

 equally good results with the scales of other fishes, such as the sprat, 

 sardine, etc. 



* Univ. California Publications, xvi. (1915) pp. 55-62 (2 figs.). 



