INTRODUCTION PROTOPLASM THE CELL 



The cytoplasm consists of a fluid matrix in which a finely 

 granular reticulum may be demonstrated. Other though less 

 constant structures are found within the cytoplasm. Such are 



the microsomes, coarse gran- 

 ules which probably belong 

 to the structure of the proto- 

 plasm itself; vacuoles, which 

 occur as spherical inclosures 

 of a more fluid substance; 

 paraplasm,* a generic term 

 which, in various cells, may 

 include all sorts of foreign 

 bodies, pigment, bacteria, in- 

 gested particles of nutritive 

 material, etc. 



The nucleus is inclosed by 

 a highly chromatic nuclear 

 membrane, within which is 

 an achromatic ground sub- 

 stance or nuclear matrix, a 

 THEORIES OF CELL STRUCTURE. fine network of achromatic 



1, alveolar structure; granules occur only &'* fibrils, and a COarse 

 at the angles formed by the alveoli. , filar network of cJiromatin fibrils, 

 structure, showing filar and interfilar mass. The cnromatin fibri l s here 

 Ine centrosome (a diplosome) is represented in 



this portion; it is surrounded by a clear at- and there present Small knot- 

 traction sphere. 3, granular structure; coarse like thickenings, Or JcaryO- 

 microsomes irregularly disposed. This portion -, -, 



contains three foreign bodies which have been somes '> wmc especially 



included by the cell, a streptococcus, a crystal, prone to OCCUr just within 

 and a spheroidal pigment mass. 4, the alveolar ^ e nuclear 

 walls are formed by regularly arranged micro- 

 somes; a vacuole is shown in this section. 5, 

 reticular structure. 



The cell is inclosed by a cell membrane, and 

 contains a central nucleus in which are shown 



the nuclear membrane, indistinct linin fibrils, ic Substance, the 

 deeply stained chromatin in coarse threads and which is closely related 



Fio. 1. DIAGRAM ILLUSTRATING THE VARIOUS 



membrane, at 

 . , . 



tne periphery Ol the nucleus. 



Within the nucleus is also a 



o-nhprnlp of rhrnmat 



to 



irregular masses (karyosomes), and a centrally ,, , . -, 



situated rmoipniiis m- nias the chromatic nuclear net- 



situated nucleolus or plasmosome. 



work. 



The typical cell also includes, usually at some point near the 

 nucleus, a small chromatic dot or centrosome, which is surrounded 

 by a clearer area, the attraction sphere. These bodies are closely 



* This term has been used by von Kupffer in an entirely different sense, as 

 synonymous with exoplasm. 



