CHAPTER II. 



Modern Steps of Progress. 



The attempts to penetrate the mysteries of the morpholo- 

 gical and chemical conditions of living cells are of comparatively 

 recent date. After R. Brown for the first time described the 

 cellular nucleus in the year 1833, and a few years later were 

 published the investigations of Schwann and of Schlciden on the 

 cellular structure of the organisms, when attention was drawn 

 by Dnjardin to the apparent structureless, semifluid contractile 

 substance of some of the lowest kinds of animal forms, called by 

 him sarcode. Soon afterwards Mohl observed (1846) the pre- 

 sence of a similar substance in plant cells, which he called 

 protoplasm. Schulze demonstrated later the chemical identity and 

 showed that this substance lies at the base of all the phenomena 

 of animal and vegetable life. Every vital act depends upon the 

 some mode or property of protoplasm, which is of albuminous 

 character, and is the tangible reality, the chemical foundation 

 of life. That was the first important generalisation in the 

 domain of biological science. — Numerous observations followed : 

 the circulation in the vegetable protoplasm and its dependence 

 upon the access of air, the division of the nucleus and, quite 

 recently, the central corpuscles were discovered, the protoplas- 

 matic nature of the chlorophyllcorpuscles was demonstrated, the 

 leukoplasts were described. Important qualities of the cyto- 

 plasm became known and the different functions of the outer 

 and inner layer (cortical layer and tonoplast) were noted. 



Attempts were even made to decipher the finer structure of 

 the cytoplasm and nucleus, and a reticular structure was dis- 

 tinguished from a hyaline and apparently uniform interfilar pro- 

 toplasm. It was further shown, that not a single chemical 

 process of importance can take place without the participation 

 of protoplasm ; even each single starch-granule has its own 

 protoplasmatic manufacturer. Protoplasm is artist and tool 

 simultaneously, it cannot be a formless albuminous slime, it 

 must possess specific organisations according to the different 

 functions it performs. In the molecular condition of protoplasm 



