Chapter III — 17 — Physical Properties 



ity. They are very easily observed in the epidermal cells of the 

 membranaceous bracts of Iris germanica and in the bulb scales of 

 Allium Cepa. These movements are observable because of the rapid 

 displacements of the lipide granules contained in the cytoplasm 

 which are seen circulating in the trabeculae between nucleus and 

 cytoplasm. The chondriosomes also are carried in the current but 

 much more slowly. Very favorable objects for the study of these 

 movements are to be found in fungi of the genus Saprolegnia and 

 in the leaf cells of Elodea canadensis. In Saprolegnia, as well as 

 these movements of circulation revealed by the displacement of 

 lipide granules and chondriosomes, there are also sometimes 

 observed displacements of an entire portion of the cytoplasm which 

 carries along with it the nucleus and vacuoles, a movement which 

 seems to be due to a general contraction of the cytoplasm. These 

 movements can be easily observed in moist-chamber cultures. The 

 observations of Lapicque, and more recently of Mangenot on 

 Spirogyra, have made clear the general nature of these movements. 

 In direct light, the cells of this alga show a hyaline cytoplasm 

 which, in addition to the ribbon-like chromatophore which will be 

 discussed later, contains, in suspension, chondriosomes in the form 

 of granules and short rods. These are arranged in rows and move 

 toward one extremity of the cell or the other. The chondriosomes 

 of neighboring veins may move in the same or opposite directions, 

 then may mingle in great agitation and soon after disperse, either 

 by all going in one direction or by different chondriosomes taking 

 different directions. These chondriosomes are being carried by 

 currents which agitate the mass of cytoplasm, currents similar to 

 those of the Plasmodium and which, like them, appear to be rapid 

 and restricted. These currents form little adjacent veins compar- 

 able in certain ways to the convection currents which agitate a 

 liquid as it is being heated. In observing the deeper regions of 

 the cell, the nucleus is seen at the center attached to the walls by 

 several strands of cytoplasm. This cytoplasm lines the internal 

 face of the wall as a thin layer surrounding the vacuole. The 

 boundary between the cytoplasm and the vacuole changes con- 

 stantly: for instance, the moving cytoplasm accumulates at one 

 point forming a protuberance which immediately disappears while 

 another appears a certain distance away, then is absorbed, and 

 so on. 



All these currents are accelerated in the presence of different 

 agents (electricity, various chemical substances, etc.) and are 

 halted by ansesthetics. 



The cytoplasm with regard to vital dyes and fixed preparations :- 



The cytoplasm is permeable to water but as long as it is in the 

 living state, it is little permeable to certain substances dissolved 

 in water. It is often said that cytoplasm is impermeable to most 

 stains. It has been known for some time, however, that certain 

 basic dyes, called vital dyes, such as neutral red, cresyl blue, Nile 

 blue and methylene blue, have the property of penetrating the 



