838 SUMMARY OF CUEEENT RESEARCHES RELATING TO 



placed for 2-12 hours. The best stains after this were dahlia and 

 fuchsin. 



A third method is by using a strong solution for 2-12 hours of 

 extract of logwood. After this mordant fuchsin is the best dye. This 

 process is improved by the addition of acids, as hydrochloric acid, 1 per 

 cent. ; gallic acid, 1/2 per cent. ; carbolic acid, 1-2 per cent. 



By these methods the author has been able to show not only cilia, 

 but tufts of them in many spirilla. The micro-organisms specially 

 alluded to are Spirillum undula, Vibrio vagula, and small vibrios. 



Impregnating Tissues by means of Methylen-blue.* — Prof. A. S. 

 Dogiel says that methylen-blue is an excellent substitute for silver 

 nitrate for the purpose of impregnating tissues such as those made up 

 of connective tissue, and also serous membranes. The method of 

 impregnation is as follows :— A 4 per cent, solution of methylen-blue is 

 made in physiological salt solution. In this is placed the piece of tissue 

 quite freshly cut out for 10-20-30 minutes, according as it is desired 

 to show merely the boundaries between the cells, or to obtain a negative 

 picture of the lymph-spaces and vessels. 



In the former case it is sufficient to leave the tissue in the solution 

 for only a few minutes ; in the second it is better to remove the super- 

 ficial epithelium from the serous membranes, and leave the tissue in the 

 solution for fifteen to thirty minutes, in order that it may be thoroughly 

 saturated with the dye. At the expiration of this time the preparation 

 is removed and transferred to a saturated solution of picrate of 

 ammonia, wherein after having been carefully washed, it is allowed to 

 stay for half an hour or longer. It is then washed again in some fresh 

 picrate of ammonia, and examined in dilute glycerin. 



If it be desired to preserve the preparation for some time, it is 

 advisable to place it in glycerin saturated with picrate of ammonia. 

 The plate shows that the method gives satisfactory results. 



Impregnation in Black of Tissues.f — M. Flot adopts the following 

 methods for impregnating tissues, wherein a coloured chemical precipi- 

 tate is formed by the reaction of two different bodies on each other, and 

 it is therefore owing to this chemical deposit that the preparations are 

 stained: — 



(1) Perchloride of iron and tannin. In this are required a concen- 

 trated solution of iron perchloride and a solution of tannin in alcohol, 

 made to a syrupy consistence. In a watch-glass are placed two drops of 

 tannin, and in another three or four drops of perchloride of iron ; both 

 are filled up with distilled water. The section previously treated with 

 hyposulphate of soda and washed is placed for a minute in the tannin, and 

 then after being passed through water, transferred to the perchloride, 

 whereby it is stained a deep black. As soon as this occurs, it is removed 

 to water and left there for five minutes. Afterwards it is mounted in 

 the usual manner. 



(2) Sulphate of copper, bichromate of potash, and extract of logwood. 

 Ten per cent, solutions of copper sulphate and of bichromate of potash 

 are prepared. Five drops of each solution are placed in a watch-glass, 

 and this is then filled up with distilled water. Another watch-glass is 

 filled with a strong solution of extract of logwood. The section is first 

 placed in the logwood solution for about five minutes, and is then 



* Arch. Mikr. Anat., xxxiii. (1889) pp. 440-5 (1 pi.), 

 t Revue Gcu. de Botanique, i. (1889) pp. 200- 1. 



