no OBSTETlih'AL niVSloLDdV. 



The teeth are developed in the interior of a cavity called the " dental 

 follicle " or " sac," by means of the elements of three germs correspond- 

 ing to the anatomical constituents of the teeth — enamel, ivory, and 

 cementum. The follicle is an oval cavity whose wall comprises two 

 layers — an external tibrons sac, and an internal gelatinous lining, at the 

 bottom of which is the ivory pulp or ijcrni. This is a prominence 

 detached from the bottom of the sac, and has exactly the shape of the 

 tooth. It is composed of a mass of delicate cellular tissue provided 

 with vessels and nerves, and on the surface a layer of elongated cells. 

 At the sunnnit of the follicle, facing this pulp, is the enamel pulp, which 

 fits accurately on the dental pulp like a cap. This is made up of 

 a small quantity of mucoid cellular tissue, covered by a layer of 

 cylindrical cells connected with the buccal epithelium by the guberna- 

 cnlnin dentis. The cetncnt otyan manifestly exists in the Foal, being 

 found at the base of the ivory germ, though it disappears quickly after 

 having performed its function. It is unnecessary in this place to enter 

 into a consideration of the development of the teeth. 



The lirer connnences to be formed at an early period in all animals, 

 appearing at the surface of the duodenum in the shape of one large 

 tubercle or two snuxll ones, according to the mnnber of lobes in the 

 organ of the adult. To these external tubercles, corresponding internal 

 ones arise from the intestinal epithelium ; the tirst increase and enclose 

 the omphalo-meseraic vein, while the second ramify in their interior 

 and form the biliary ducts. 



The liver grows rapidly, and when about one- third of the period of 

 gestation has elapsed it nearly tills the abdominal cavity. At a later 

 date this increase is less nuirked, although when gestation is nearly 

 terminated the gland is proportionately more voluminous than in the 

 adult. 



The pa}icrcas, like the salivary glands, is tirst seen as a solid cellular 

 tubercle, which is subsequently hollowed out by ramescent cavities. 



The spleen is developed about the second month, on the great curva- 

 ture of the stomach ; it would appear to be formed at the same time as 

 the pancreas, in a band extending from the stomach to the duodenum ; 

 but it is separated from the pancreas and becomes attached to the 

 stomach, where its elements assume the character of splenic tissue. 



The Genito-urinari/ Onjans. 



The genito-urinary organs are related to each other in their develop- 

 ment, and have some parts in common. Immediately after the 

 formation of the intestines, these organs are anticipated by the Woljtfion 

 bodies or prifiiordial kidnei/s. These are glandular masses extending 

 in front, or one on each side, of the vertebras from the heart to the 

 pelvis. They are composed of small transversely disposed tubtili 

 filled with a white Huid, 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 peritonetnn, the Woltlian bodies are attached by two 

 folds of serous membrane — one, the anterior, named the diapJiraijmatic 

 ligament of the Wo[rfla)t bodies; and the other, posterior, the lumbar 

 ligayncnt of the Wolffian bodies. These organs secrete at tirst 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 



