CHAPTER IV 

 TISSUES 



To grasp an understanding of the various tissues 

 properly, a brief description of the cells from which 

 they are developed, embryologically, will be necessary. 



The Ovum. The ovary secretes a cell, the original 

 cell of the female human body, called the ovum. The 

 ovum consists of a limiting wall, the vitelline membrane, 

 enclosing the protoplasm, vitellus, which consists of 

 two parts the dentoplasm or nutritive yolk, and the 

 animal protoplasm or formative yolk. Within the 

 vitellus is found the nucleus or germinal vesicle, which 

 contains the nucleolus or germinal spot. 



Before an ovum can develop into an offspring it 

 must undergo numerous complex changes. The two 

 most important phenomena are defined as maturation 

 and fertilization. 



Maturation. Maturation or ripening is the process 

 taking place in the ovum, which prepares it for the 

 reception of the male element spermatazoon, where 

 its contained chromatin and a small part of the proto- 

 plasm are collected into the form of two minute 

 structures called polar bodies, when a modified cell 

 reproduction or karyokinesis occurs. This reproduc- 

 tion must take place before ova can be fertilized. 



Fertilization. This is the process in which the male 

 and female units the ovum and spermatozoon unite 

 to form a complete and perfect cell, by division, 

 which ultimately develops into cells which form the 

 tissues of the whole body. 



The male element or spermatozoon or spermium con- 

 sists of a head, middle-piece, and tail. After entering 



