41 



t 



green color. Sections mounted in water several weeks ago have 

 retained this color thus far. 



CoraHin colors the mucilage a dull pink or red, and nigrosin 

 stains all the large drops in the hairs steel-blue, the surrounding 

 plasma faintly yellow, and the mucilage in the sacs, as well as 

 outside of them, blue also, but its color usually disappears after 

 it has remained for several weeks in glycerin, while the mucilage 

 in the hairs has not thus far (for about one-half a year) lost its 

 color. The stained mucilage masses may be forced out of the 

 hair by pressure on the cover-glass, when it will be noted that 

 the crushed wall of the hair invariably breaks up into a continu- 

 ous spiral band. It takes considerable time to stain the mucilage 

 with nigrosin, for as long as the cell lives the coloring matter is not 

 admitted. I observed repeatedly that hairs placed in a nigrosin 

 solution, so dark that it was almost opaque, stayed alive for sev- 

 eral days, i. e., their plasma kept moving and the mucilage 

 remained unstained. 



Methylene blue, on the other hand, passes through the cell 

 wall and the living plasma.* A drop of the concentrated solu- 

 tion was diluted with 5 cc. of water and some living hairs with 

 well defined mucilage drops w^ere placed in it. After two hours 

 most of the mucilage masses had become distinctly blue, while 

 the motion of the colorless plasma had ceased in nearly all the 

 hairs. Some of these sections were then placed in water, and 

 after a short while the plasma again became active, and after three 

 days the mucilage in most of the hairs had lost its blue color; in 

 some of the hairs, however, it was permanently stained, and the 

 plasma did not recover. 



Very interesting observations were made when some young 

 hairs were treated wdth acetic acid. As soon as the acid was 

 applied, the mucilage began to expand rapidly, and simultaneous- 

 ly a swelling of the entire hair was noticed ; the mucilage crowded 

 back the vacuoles and the strands of protoplasm towards both 

 ends of the hair, until the entire cavity was filled with an almost 

 transparent mass ; then, sometimes at one point, sometimes at 

 several, a slight swelling of the outer layer of the wall took place» 

 which gradually increased until, at length, there was an entire 



^ ^ — *^ 



'* Cf. W. Pfeffer, Unters. a. d. hot. Inst, zu Tiibingen, II, 2. lift. 



