374 ANIMAL BIOLOGY. 



vertebrate which differentiates from the rest, and forms a chain of 

 ganglia, connected with the cerebro- spinal nerves. 



Systole. The contraction of the ventricle or other part of the heart ; the 

 relaxation is called diastole. 



TelolecithaL See Alecithal. 



Tendon. A fibrous band of connective tissue by which a muscle is 



attached to the endoskeleton. 



Tergum. The dorsal part of the exoskeleton of the crayfish and cock- 

 roach. Hence this dorsal region is often termed the tergal region, as 



opposed to the ventral or sternal region. 

 Testes. (1) The male generative organs. (2) The posterior divisions of 



the corpora quadrigemina of the mammalian brain. 

 Thorax. (1) The part of the coelom in front of the diaphragm in the 



vertebrate. (2) The mid-region of the body in the crayfish and 



cockroach. 

 Traoecula. (1) A band of tissue. (2) Special bands of tissue in the 



developing skull. 

 Trochanter. (1) A process of the upper part of the femur. There are 



three such processes in the rabbit. (2) The second joint in the leg 



of the cockroach. 

 Typnlosole. A longitudinal fold projecting inward into the intestine. 



Umbilicus. (1) The inferior and superior umbilicus are small holes in the 

 bird's feathers ; (2) The umbilical vesicle and cord are foetal structures in 

 the rabbit. 



Urinogenital System. Sometimes called urogenital ; the reproductive and 

 excretory organs, the ducts of which are closely related in the verte- 

 brate . 



Utriculus. (1) A division of the vertebrate organ of hearing ; (2) A finger- 

 like process of the mushroom gland of the cockroach. 



Vascular. Connected with the blood. The vascular system is the circu- 

 latory system. An organ is vascular when it is richly supplied with 

 blood-vessels. 



Venous. The blood is venous when the corpuscles have given up their free 

 oxygen to the tissues, and the plasma is laden with carbonic acid. 

 The pulmonary artery contains venous blood. 



Ventricle. (1) The fleshy part of the heart, subdivided in the rabbit and 

 the fowl ; (2) A cavity of the brain, e.g. 4th ventricle, lateral ventricle. 



Vesicle. (1) The primitive vesicles of the brain are the anterior enlargements 

 of the neural tube ; (2) The auditory vesicle is the auditory sac ; (3) 

 The germinal vesicle is the nuclear part of the ovum ; (4) The umbilical 

 vesicle is a provisional fcetal organ in the rabbit ; (5) The vesiculce 

 seminales are accessory parts of the male reproductive organs. 



