CHANGES IN THE OVUM. 



103 



of the intestines, these organs are anticipated by the Wolffian bodies or 

 primordial kidneys. These are glandular organs extending in front, or 

 one on each side, of the vertebrae, from the heart to the pelvis. They 

 are composed of small transversely disposed tubuli filled with a white 

 fluid, and opening into a common duct running parallel to the spine, 

 which again enters, inferiorly, that portion of the allantois which becomes 

 the bladder. The duct is formed before the tubuli, and is one of the 

 earliest developed structures in the embryo. Placed behind the perito- 

 neum, the Wolffian bodies are attached by two folds of serous membrane : 

 one, the anterior, named the diaphragmatic ligament of the Wolffian bodies ; 

 and the other, posterior, the lumbar ligament of the Wolffian bodies. These 

 organs secrete at first a fluid resembling wine, though their function is 

 soon greatly modified, as they are not long in becoming atrophied ; then 

 a portion serves for the development of the genital organs, while another 

 gives rise to organs whose use is not exactly known, such as the Rosen- 

 miiller organ, which is very developed in the equine foetus, and the canals 

 of Gaertner visible in the Cow 



Male Foetus of the Mare at Five-and a Half Months: the Abdomen opened and 

 Testicles exposed. 



I, Thighs ; 2, Penis, neither Scrotum nor Prepuce are yet foj-med ; 3, Bladder, with the two 

 UmbiHcal Arteries ; 4, Abdominal Parietes ; 5, Douglas' Foramen, with the two Afferent 

 Canals, 3, i5i ; 6, Kidneys ; 7, Supra-renal Capsules; 8, Rectum ; 9, Mesorchis or Spermatic 

 Cord ; a, Gubemaculum Hunterii ; «i, Intenial Inguinal Ring ; b, b. Efferent Ducts ; c, c, 

 Testicles ; d, d, Pampiniform Plexus. 



With regard to the urinary organs, we have mentioned how the 

 allantois was derived from the terminal portion of the intestine ; it only 

 now remains to add that the urinary bladder is derived from the abdomi- 

 nal portion of the allantois, which is merely a dilatation of that sac. 

 During fcetal life, the bladder is extended by the urachus to the umbilical 

 ring ; but after birth this canal is obliterated, and the bladder retires to 

 the bottom of the pelvic cavity. 



The kidneys appear a long time after the Wolffian bodies. They show 

 themselves in the form of two culs-de-sac, constituted by the upper wall of 



