62 



HISTOLOGY 



nucleus is unspecialized and similar to the other tissue nuclei in its 

 neighborhood. 



The characteristic feature is the cytoplasm. This is drawn out into 

 tapering strands, of which two to four or five are usually present in the 

 plane of section. These arms of cytoplasm meet the arms from other 

 cells and form all together a network which fills the space and holds every- 

 thing together by the union of the arm-like processes (Fig. 64). 



As before stated, the cytoplasm is not in itself strong enough to 

 do the work that these tissues will be called upon to do. The required 

 strength is furnished by bundles of fine thread-like bodies of great 

 strength, which appear about the cytoplasmic processes. These threads 

 are formed by the cytoplasm and controlled by it. They extend from 



FIG. 64. Part of a section across the umbilical cord of an embryo sheep. Under the epithe- 

 lium are seen the young connective-tissue cells with branching cell bodies that form a reticu- 

 lum. These cells divide by mitosis, two stages of which may be seen in the figure. 



cell to cell and by becoming united to similar neighboring bundles of 

 threads at various angles, they form a very strong network of tissue. 

 They are not strongly formed at this time in the specimen. 



The extreme adaptability of such a tissue forms an interesting study 

 in early embryonic sections. The cells which ordinarily reach and hold 

 in all directions are, when placed in some special position, rapidly modi- 

 fied to meet any unusual strain from any given direction. Thus, close 

 to the epidermis, they flatten out in a plane parallel to the surface to pro- 

 tect the parts from injury when stretched or punched. Around the blood 

 vessels they elongate into two -armed spindles, which encircle the tube and 

 hold it while the blood comes in waves and spurts against its walls. 



The growth of this tissue is performed by mitotic division, as shown in 

 two stages in Figure 64. When fully developed, most of it forms the 

 so-called lax connective tissue between muscle and skin and the fascia of 

 muscles. 



