31 8 Veterinary Obstetrics 



gland do not ossify, the very dense tunica albuginea affords a 

 degree of compression of a somewhat analogous character. 



We may then state that, so far as we know, teeth are always 

 liable to result whenever limited sacs of epiblast become invagi- 

 nated into mesoblast, and become incarcerated and separated 

 from the general epiblastic layer, while the surrounding meso- 

 blast is converted into bone or is bound down by firm layers of 

 unyielding connective or other dense tissues. 



The Liver. 



The liver of the embryo appears about the end of the second 

 week as an outgrowth from the inferior wall of the intestine just 

 beyond the dilation which marks the future stomach. The for- 

 mation of the liver resembles in many respects that of the lungs, 

 the outgrowth becoming enlarged at its distal end, while the 

 proximal portion becomes narrowed to constitute the bile duct. 

 The liver is the most conspicuous of all the glands in the embryo 

 and, at the time of birth, constitutes the largest and heaviest 

 portion of the internal viscera. In volume and weight, it is equal 

 to the entire intestinal tract, with the lungs and heart added. 



The Pancreas. 



The pancreas arises at about the same time as the liver, as an 

 infundibulum from the anterior wall of the duodenum, and is 

 lodged in the tissue of the mesentery between the intestine and 

 dorsal wall. The gland quickl}- divides up into lobules, from 

 which the acini and ducts are formed. 



