MORPHOLOGY OF THE CELL 



35 



Finer Structure of the Cytoplasm. — Protoplasm occurs in so many 

 different forms, and undergoes so many changes during its normal activi- 

 ties, that agreement among careful students as to its intimate structure 

 was long delayed. With this debate the student is only partially con- 



FiG. 21. — Cell bridges, or strands of protoplasm connecting the cells, in the skin of a 



salamander. (After Flemming.) 



cerned. It seems now fairly safe to say that the most common form of 

 protoplasm is that of an emulsion. That is, it is composed of minute 

 spheres of liquid or semi-liquid matter suspended in another liquid or 



Fig. 22. — Diagram of an emulsion, illustrating the physical structure of a very common 

 kind of protoplasm. The spheres are alveoli, the substance between them the inter- 

 alveolar substance. 



semi-liquid substance. A correct idea of the phj-sical structure of pro- 

 toplasm may be gained by imagining a quantity of marbles of various 

 sizes poured into a vessel of syrup, and then supposing the marbles to 

 become hquid without changing their relations to each other. The 



