160 G. L. Kite 



to offer an appreciable resistance to a glass needle a micron or less in 

 diameter. The disagreement among investigators concerning the 

 presence of a sarcolemma is due to the fact that it is transparent and 

 that its refractive and dispersive powers are so nearly the same as 

 those of water. Instead of being the delicate structure of the con- 

 ventional descriptions, the sarcolemma of the striped muscle cell of 

 Necturus exhibits physical properties that are very similar to those of 

 the vitelline membrane of an echinoderm egg. 



If a concentrated solution of isamin blue made by boiling in dis- 

 tilled water or .8 per cent sodium chloride be added to freshly teased 

 muscle cells, blue staining of the sarcolemma occurs in ten to fifteen 

 minutes. 



An Epidermal Cell. The epidermal cells are embedded in an 

 intercellular gel of extremely high viscosity and considerable elas- 

 ticity. The substance is tough but softer than many nuclear mem- 

 branes and shows a relatively high absorptive power. It is also quite 

 turbid. A few globules and granules, varying in size from about 

 one to four microns, that can be easily stained with diethyl-safranin- 

 azo-dimethyl-anilin are to be seen scattered through the intercellular 



gel- 



The whole cell substance is a gel of even higher rigidity than the 

 muscle substance of the same animal. Small pieces cut out of the 

 nucleus or cytoplasm, in distilled water or .8 per cent sodium chloride, 

 show no appreciable change. 



The cytoplasm exhibits a high absorptive power and a definite 

 elasticity. Very small granules that seem to be denser cytoplasmic 

 areas are to be seen scattered throughout the turbid cytoplasm. 

 Many cells show radially arranged fibrils, in the outer part of the 

 cytoplasm, which can be partially freed from the surrounding gel by 

 dissection. Such a fibril is physically and optically more dense than 

 the remainder of the cytoplasm. 



The nuclear membrane is thin, clear, and* quite cohesive and elas- 

 tic, and 1ms a different index of refraction from the cytoplasm and 

 nucleus. 



The nuclear gel is of a higher viscosity than the cytoplasm. The 

 appearance of a network in the optical image of the nucleus is due to 

 concentrated areas in the form of granules and imperfect threads which 

 are not sharply separated from, but grade into, the surrounding diluter 



