ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 849 



the vapour of perruthenic acid the membrane blackens, and the calyciform 

 cells are the first to become black, the mucigen alone being coloured, and 

 the vacuoles remaining colourless. 



Methylen-blue Staining.* — Dr. C. Arnstein has examined methylen- 

 blue staining on the living frog by injecting into the vena cutanea magna 

 1 cc. of a saturated solution of this dye. The tongue and palate were 

 stained at once, the nerves were not coloured, the dye being found in the 

 blood-vessels only. One or two hours later the nervelets in the taste 

 papillae and the thick plexuses of the palate are seen to be blue. The 

 motor-nerve terminations become stained still later. Eeichert's pleural 

 muscle may be used to determine the appearance of the stain. " One muscle 

 is removed in two hours, and if insufficiently stained, the second muscle is 

 inspected after another two hours. The eye-muscles are treated in a similar 

 manner, one ball being removed at an early stage, the other at the end of 

 the experiment." Sometimes, however, these muscles do not stain at all, 

 and even if the nerves are well stained they remain so only for a short 

 time, 5-10 minutes about. To retain the colour it is necessary to fix the 

 methylen-blue with iodine, and this reaction turns the blue to brown. A 

 1 per cent, watery solution of iodide of potassium in iodine dissolved to 

 saturation, is used. The solution is injected through the blood circulation 

 system, and serves also to remove the blood. The frog may be allowed to 

 remain in this solution. The necessary pieces are then cut out and placed in 

 the iodine solution for 6-12 hours, after which the iodine is removed by a 

 thorough washing. Next day the black-brown or grey nerves stand out 

 clearly on a colourless background. Mount in acidulated glycerin. Be- 

 sides nerves and nerve epithelia, certain other elements are stained during 

 life, such as the cells in the gustatory papillae of the frog's tongue, 

 certain cells of the palate which lie between the unstained mucous cells, the 

 gland-cells of the membrana nictitans, the cells of the propria in the lingual 

 glands, which as isolation preparations treated with iodine, appears as 

 brown ramified plates. The cells of the cornea, too, are partially stained if 

 the ball be allowed to remain in situ for a short time after death. The 

 cornea is then excised and thrown into the iodine solution, but the staining 

 of the corneal cells only occurs when the plexus has been stained during 

 life. Over gold chloride it has the advantage of staining only the cells 

 and their prolongations, and not the lymph channels of the connective 

 tissue cells ; those which show the most affinity for methylen-blue are the 

 fat-cells. At one time they stain deeply, even when the nerves are yet 

 uncoloured ; later they seem to lose their colour. Sometimes after death 

 they are again very beautifully stained. During life, many red blood- 

 corpuscles show a nuclear stain, but the white corpuscles do not take up 

 any dye. 



New Green Dye.f — Dr. W. Krause has been examining a double zinc 

 salt of thiophin-green (O21H24N2OS) as to its utility for microscopical 

 purposes. It is easily soluble in water, alcohol, oil of cloves, chloroform, 

 with a beautiful green colour in which there is a trace of blue. It may be 

 used in conjunction with carmine as a double stain. Fresh tissue hardened 

 in absolute alcohol. Staining with borax-carmine in toto, washing, spirit, 

 chloroform-paraffin, paraffin. Sections 0*005 mm. thick fixed to the slide. 

 Collodion, clove oil, paraffin dissolved in benzol, and then removed with 

 absolute alcohol. A drop of a concentrated watery solution of thiophin- 

 green is allowed to act on the moist section for some minutes. It is then 



* Anat. Anzeig., ii. (1887) pp. 125-35. 



t Internat. Monatschr. f. Anat. u. Physiol., iv. (1887) 2 pp. 



