THE URINOGENITAL SYSTEM 



403 



gland at this time, but docs not open into the cloaca. Indeed, 

 the opening is not established until after the hen is six months 

 old (Gasser.) 



Fig. 231. — Photograph of a cross-section of an embryo of 8 days through the 



ostia tubse abdominaha. 



a. A. S., Neck of abdominal air-sac. O. T. a., Ostium tubse abdominale. 

 M's't.ac, Accessory mesentery, pi. C. r., 1., Right and left pleural cavities. 

 Rec. pn. ent. r., Right pneumato-enteric recess. V. c. a. 1., Left anterior 

 vena cava. R., rib. Other abbreviations as before. 



IV. The Suprarenal Capsules 



The suprarenals of the hen are situated medial to the anterior 

 lobe of the kidney, in the neighborhood of the gonad and vena 

 cava inferior. They have a length of about 8-10 mm. The 

 substance consists of two kinds of cords of cells, known respec- 

 tively as cortical and medullary cords, irregularly intermingled: 

 the so-called cortical cords make up the bulk of the substance, 

 and the medullary cords occur in the meshes of the cortical cords. 



