CHAPTER IL 
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 Schleiden on the 
cellular structure of the organisms, when attention was drawn 
by Dujardin 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 ( cort ical 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 
