GENERAL INTERNAL ORGANIZATION 



47 



p-c a 



b.m-c. 



L.p-a 



t.a. 



their identity can only be recognized by a thorough study of Com- 

 parative Anatomy and Embryology. 



The Coelome and Viscera. — When the ventral body wall of the 

 frog is opened, there is disclosed a spacious cavity, the coslome, con- 

 taining the digestive organs, heart, lungs, and other viscera (Figs. 

 23 and 27). The digestive 

 tract enters the anterior end 

 of the cavity as the eso- 

 phagus, leading directly into 

 the stomach, which is followed 

 by the small intestine, the 

 large intestine, and the cloaca. 

 The liver is connected with 

 the beginning of the small 

 intestine by the hile duct. 

 The pancreas, which secretes 

 the pancreatic juice used in 

 digestion, lies around the 

 bile duct into which open the 

 pancreatic ducts. The kidneys 

 and their ducts, the ureters, 

 lie on the dorsal side of the 

 coelomic cavity, separated 

 from the body wall by an 

 extensive lymph space, the 

 suhvertehral lymph sinus 

 (Fig. 19). The reproductive 

 organs, ovaries or testes, are 

 attached to the ventral face 

 of either kidney. Attached 

 to the body wall at the an- 

 terior ends of the kidneys 

 are masses of finger-shaped 

 structures known as the 

 fat-bodies which have the 

 nutrient material 



Fig. 



27. — Viscera of frog from ventral 

 view. 



ab.v., abdominal vein; b.m-c, brachial mus- 

 culo-cutaneous vein; b.w., body wall; bl., urin- 

 ary bladder; c.a., carotid artery; e.j., external 

 jugular vein; in., internal jugular vein; int., 

 small intestine: La., left auricle; l.i., large 

 intestine; I. p-c, left pre-caval vein; Ig., lung; 

 Iv., Liver; mh., mylohyoid muscle; p-ca., 

 pulmo-cutaneous artery; pc, pericardium; r.a., 

 right auricle; s.a., systemic artery; sp., spleen; 

 St., stomach; t., testis; t.a., truncus arteriosus; 

 th., thyroid gland; tm., thymus gland; v., ven- 

 tricle. (Redrawn with modifications from 

 Howes, "Atlas of Zootomy," copyright, 1902, by 

 Macmillan and Co., Ltd., printed by permission. 



function of storing a reserve of 

 They have no known functional relation to 

 the urino-genital system. Along the ventral face of each kidney 

 are elongated strips of tissue, the adrenal bodies, which have the 

 function of producing a chemical substance, adrenalin, that passes 

 into the blood. Like the fat-bodies, the adrenals have no known 



