Protoplasm. 29 



examples of these transition-substances which are more 

 commonly known may be given, e.g. urea, a nitrogenous 

 derivative excreted by the kidney, bile-acids, ammonia, and 

 various ammoniacal salts, tannin, wax, and many vegetal 

 acids and alkaloids. 1 



SECTION II. MORPHOLOGY AND PHYSIOLOGY OF 

 PROTOPLASM. 



Protoplasm (-n-p^ro<s 'first,' TrAarr/xa 'formed substance ')> 

 when examined in large quantity by the naked eye, appears 

 as a colourless, more or less transparent jelly. In nature it 

 however occurs much more frequently subdivided into ex- 

 tremely minute pieces, resembling each other in general 

 structure and appearance. To study these separate par- 

 ticles, or cells as they are termed, high magnifying powers 

 of the microscope are required. When so examined proto- 

 plasm is found to consist of a clear, glassy, or finely granular 

 soft substance, in which there is frequently to be distinguished 

 an outer layer or ectoplasm, always more transparent than 

 the inner, more granular endoplasm. In consistence proto- 

 plasm varies very greatly. 



In intimate structure it consists of a homogeneous 

 portion or matrix in which are imbedded granules (fig. i). 

 Minute droplets of water also occur (more abundantly in 

 plant than in animal protoplasm), which go by the name of 



1 It is to be distinctly understood that a memory-knowledge of the 

 characters of the substances entering into the composition of protoplasm 

 is of little value, unless coupled with a practical knowledge gained by 

 actual observation and experiment in the laboratory. This synopsis of 

 the characters of proteids and other organic compounds is intended for 

 reference. It is suggested that one or two of the most striking pecu- 

 liarities of the substances, once seen, should be kept in mind, and that 

 the other characters should be learnt gradually and unconsciously as 

 familiarity with the substances themselves is obtained. That know- 

 ledge consists in being able to repeat a list of peculiarities by heart is 

 one of the most mischievous delusions of modern education. 



