922 TEXTBOOK OF ZOOLOGY 



Vascular system (vas'kuler), the circulatory system. 



Vascular tissue (vas'kuler), fluid tissue consisting of cells known as corpuscles 



in a fluid medium, plasma. 

 Vein (van), the larger blood vessels leading to the heart. 



Ventral (ven'tral), side away from the back; literally belly; opposite to dorsal. 

 Villus (vil'us), a fingerlike, vascular process of the internal lining of the 



small intestine. 

 Vitamins (vi'tamins), substances which occur in small amounts in numerous 



foods and are essential regulatory substances for the animal body. 

 Vitelline (vitel'lin), the outer membrane of an egg. 

 Vitreous (vit'reus), glassy in appearance. 

 Viviparous (vi vip'a rus), the retention and development of the egg in the 



mother's body and nourishment of the embryo from the blood of the 



mother. 

 Volant (vo'lant), able to fly. 



Zoogeography (z6 6 je og'rafi), the study of the geographical distribution of 



animals. 

 Zoology (zoo'loji) (animal biologj^), the study of the science which treats 



of animals. 

 Zygote (zi'got), a fertilized egg, or embryo, after fertilization. 

 Zymogen (zi'm6jen), a pre-enzyme; a substance which is produced in a gland 



cell and becomes an enzyme when it is discharged and activated by some 



other substance, perhaps another enzyme. 



