WITH THE MICROSCOPE. 163 



flow to and from the germinal or living matter, and the altered 

 tension thus caused in. the cell. Ciliary motion is not dependent 

 upon nervous action, nor is it due to any disturbance in the sur- 

 rounding medium. It cannot, I think, be regarded as a. vital move- 

 ment, although it is probably due to changes which are consequent 

 upon vital phenomena. Cilia consist of " formed material." In 

 the immediate vicinity of ciliated cells are sometimes observed 

 cells with open mouths, out of which mucus and various substances, 

 formed or secreted in the interior of the cell, pass. In the forma- 

 tion of these products, nutrient matter from the blood, after passing 

 through the attached extremity of the cell, is probably absorbed by 

 the living matter. At the same time the outermost portion of the 

 latter becomes converted in the peculiar contents of the cell, and 

 thus the formed matter which has been already produced becomes 

 pushed towards the orifice. See the new edition of " The Physio- 

 logical Anatomy and Physiology of Man." I think that the move- 

 ments of cilia are brought about by a somewhat similar series of 

 changes, in which the germinal or living matter, usually termed 

 " nucleus," plays the active and most important part. 



OF DEMONSTRATING THE TISSUES OF PLANTS. 



258. Examination of Vegetable Tissues. The examination of 

 vegetable tissues is conducted upon the same general principles as 

 that of animal textures. The spiral vessels of plants can in many 

 instances be obtained by boiling the stem of the plant for some time 

 in water. Those of rhubarb are very large, and may be selected for 

 examination. 



The spiral vessels in leaves may be beautifully shown by allow- 

 ing some coloured fluid to enter them. If the stalk be placed in 

 the fluid and evaporation from the surface of the leaf be. encouraged 

 by exposure in a warm place, the fluid will enter the vessels. If 

 carmine fluid, p. 109, be used, the germinaj matter of the cells near 

 the vessels is stained at the same time that the tubes are injected. 



Thin sections of soft vegetable tissues in any direction may be 

 very easily obtained with a very sharp knife. The method of 

 cutting thin sections of woods has been already referred to in p. 84. 

 The cellular tissues of plants (certain leaves, flowers, fruits) are 

 softened and at length destroyed by weak nitric and hydrochloric 

 acid (one part of acid to from twenty to fifty of water), while the 

 fibrous and vascular textures remain behind, constituting the skeleton 

 of the leaf, flower, calyx, or fruit. 



M 2 



