20 



HITCHCOCK'S ANATOMY 



Fig. 10. 



tissues in animals and vegetables are made up. This is called 

 cytogenesis. The increase usually takes place by duplicative 

 subdivision, which is shown on Fig. 10. The cell a a first 

 becomes elongated, as at 6, and then it divides at c c. The 

 subdivision going on will give an increase in lapid ratio — 2, 

 4, 8, 16, 32, etc. Fig. 11 shows an example of this division, 



A, B, C, D, in its earlier 

 stages, and E, F, G, H, in 

 its more advanced condition. 

 Sometimes cells multiply by 

 the development of new cells 

 in the interior In this case 

 the nucleus subdivides into 

 two or more portions, which 

 at length fill the original cell, 

 as is shown in Fig. 12. Some- 

 times cells are formed by the 

 expansion of homogeneous 



granules into cells ; or they are even produced in the midst of 

 a formative fluid (called a blastema), poured out from the blood. 



Describe the mode of formation as illustrated in Figures 11 and 12. What is tho 

 Blastema ? 



