THE FCETUS. 197 



fact neither labia nor scrotum, and the sub-pubic prolongation is alike 

 in all specimens. 



500. The umbilicus. Properly speaking, there is no navel until 

 the thirtieth or fortieth day, and the cord merely proceeds to be 

 lost beneath the visceral mass of the abdomen. However, the 

 parietes of the abdomen, gradually increasing towards the omphalo- 

 placental stem, soon afterwards give birth to it. 



501. After the sixth week, or the fiftieth day, the organisation of 

 the embryo becomes rapidly perfected. The eyes become more 

 convex; a very distinct palpebral circle soon afterwards surrounds 

 them; the two extremes of the vertical diameter of this circle, by 

 gradually approaching each other, soon give it the form of an 

 ellipse, and thenceforth the two angles of the eye are observed to 

 exist. In nine or ten weeks at latest, the edges of the eyelids are 

 in contact, and so closely in some specimens, that several authors 

 have supposed that adhesion had taken place between them. Pre- 

 viously to coming in contact they were thin and sharp; but their thick- 

 ness now exceeds that of the eyelids themselves; they completely 

 cover the front of the eye, but are so transparent that its color 

 may be easily distinguished through them. The central spot before 

 mentioned grows yellow and enlarges; one is easily convinced that 

 it constitutes the cornea, and that its posterior surface is in contact 

 •with a substance of the same color. The blackish circle is also 

 enlarged, and being extended farther backwards, is found to belong 

 to the sclerotica, and that its tint depends upon the substance that 

 lines it internally. 



502. The nose, particularly, undergoes remarkable alterations: 

 the protuberance which it forms above the lip, increasing by degrees, 

 forces its anterior opening to incline gradually downwards. Its in- 

 ternal surface, which until the fifth week composes a part of the 

 buccal cavity, begins in the course of the sixth to be separated from it. 



503. The mouth does not undergo any essential change; its 

 depth increases; the tongue grows larger and thinner, the lower 

 jaw projects more, which renders the anterior cervical notch more 

 manifest; the lips are more distinct, more isolated, but their form 

 is the same. 



504. The external ear, reduced to the appearance of a leech 

 bite, in an embryo of four or five weeks, soon acquires its proper 

 characters. Every part of its concha is unfolded. After the tragus 

 and anti-tragus, we observe the slit of the helix to appear, and con- 

 sequently the concha. The lobule soon manifests itself as well as 

 the rest of the helix, with which it is continuous; and lastly, the 

 anti-helix itself is visible as early as the seventieth diay. Although 



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