101 SUMMARY OF CURRENT RESEARCHES RELATING TO 



embryos about 3 mm. long, at which stage, i.e., shortly after the closure 

 of the medullary folds, there is no visible differentiation of the nerve 

 elements. After carefully dissecting it out, the piece of tissue is re- 

 moved by a fine pipette to a cover-slip upon which is a drop of lymph 

 freshly drawn from one of the lymph-sacs of an adult frog. The lymph 

 clots very quickly, holding the tissue in a fixed position. The cover-slip 

 is then inverted over a hollow slide, and the rim sealed with paraffin. 

 When reasonable aseptic precautions are taken, tissues will live under 

 these conditions for a week, and in some cases specimens have been kept 

 alive for nearly four weeks. Such specimens may be examined from 

 day to day under high powers. 



Cultivation of Treponema pallidum.* — C. Levaditi and J. Mcintosh 

 have obtained cultivations of Spirochetes by means of the following 

 method. They inserted collodion bags charged with infected material 

 into the peritoneal sac of monkeys. The material used was obtained 

 from syphilised monkeys. From the cultures thus made were obtained 

 organisms morphologically identical with Treponema pallidum, but with- 

 out pathogenic power. 



(2) Preparing- Objects. 



New Method of Fixation.! — Wl. Rudnew places pieces of freshly 

 killed animals in the ordinary ether-alcohol solution of celloidin, and 

 after 3 or 4 weeks removes to thick celloidin solution. The pieces are 

 then stuck on wood-blocks and hardened in 70 p.c. alcohol, and sec- 

 tioned in the usual way. Unlike most inventors, the author does not 

 claim that this method is perfect : indeed he admits that it has defects 

 which he hopes to remedy, but in the title of the paper points out that 

 it is specially adapted for the study of the nervous system. 



Fixation and Preparation of Nematohelminthes4 — E. Andre 

 finds that boiling water gives the best results. When small the animals 

 should be placed in a capsule and boiling water poured over them ; this 

 should not be allowed to act longer than the fraction of a second, and 

 then the animals must be plunged into cold water. Large worms should 

 be placed in a glass tube of a diameter a little larger than that of the 

 animal. The tube is plunged into boiling water, and after one or two 

 seconds transferred to cold water. If these large worms are to be 

 sectioned they must be cut up into lengths of several centimetres before 

 immersing in the appropriate fluid. For staining in toto an alcohol 

 fluid is recommended, for the reason that while hot water is a fixative it 

 is in no sense a preservative. 



Small thread-worms, to be mounted whole as microscopical specimens, 

 should be transferred after fixation to the following medium : distilled 

 water 80, glycerin 10, formol 10, placed in a watch-glass or capsule. 

 The vessel should be uncovered but protected from dust. When the 

 fluid has evaporated to the extent of several cubic centimetres the 

 animals may be mounted in glycerin or glycerin-jelly. This method of 



* Ann. Inst. Pasteur., xxi. (1907) pp. 784-97 (2 pis.) 

 f Zeitschr. wiss. Mikrosk., xxi v. (1907) pp. 243-53. 

 % Tom. cit., pp. 278-9. 



