6 ELEMENTS OF HISTOLOGY. [Chap. i. 



multinucleated cell of the bone marrow myeloplax 

 some of which surpass in size even the ganglion cells. 

 The same holds good of the nucleus. Between the 

 nucleus of a ganglion cell of about -^^ to y^Vrr ^ an 

 inch in diameter and the nucleus of a white blood 

 corpuscle of about -^j^ to 10 ^ 00 of an inch and less 

 there are all intermediate sizes. 



6. Protoplasm is a transparent homogeneous or 

 granular-looking substance. On very careful examina- 

 tion with good and high powers, and especially when 

 examined with certain reagents, in many instances it 

 shows a more or less definite structure, composed of 

 fibrils, more or less regular, and in some instances 

 grouped into a honeycombed or fibrillar reticulum 

 in the meshes of which is a homogeneous interstitial 

 substance (Heitzmann). The closer the meshes of the 

 reticulum, the less of this interstitial substance, and the 

 more regularly granular does it appear. In the meshes 

 of the reticulum, however, may be included larger or 

 smaller granules of fat, pigment, or other material. 

 Water makes protoplasm swell up, and ultimately 

 become disintegrated ; so do dilute acids and alkalies. 

 All substances that coagulate proteids have the same 

 effect on protoplasm. 



7. The nucleus, the size of which is generally in 

 proportion to that of the cell, is usually spherical or 

 oval. It is composed of a more or less distinct invest- 

 ing cuticle and the nuclear contents, which are in the 

 ripe state arranged as an irregular or regular network, 

 the parts of which may be uniform fibrils or septa, or 

 irregularly-shaped trabeculae. In the life history of 

 each nucleus there may be stages in which one or more 

 clumps or nucleoli are present in the nuclear network. 

 The substance of the nucleus differs chemically from 

 that of the cell, the former consisting of nuclein. 



Immediately before division the nuclear membrane 

 disappears, and also immediately after division the 



