172 APPENDAGES OF THE FCETUS. 



end of giving time to nature to establish, with her accustomed gen- 

 tleness and regularity, the permanent means of nutrition in the ova 

 of mammiferous animals. From the moment of fecundation until 

 the ovule is found in immediate contact with the inner surface of 

 the womb, the product of human conception is in almost all respects 

 similar to the egg of a bird: like it, free, and independent of every 

 part of the mother, it must contain whatever is necessary within 

 itself; it must contain a substance, by the expenditure of which the 

 growth of the embryo can be effected, just as the chick must enclose 

 within its shell a material subservient to its evolution. But in one 

 this arrangement is only transient, while in the other it remains until 

 the embryo is hatched: but this difference depends upon this, that 

 in the former, incubation is performed in the interior of a living or- 

 gan, an organ capable of distributing nutritive matter in abundance 

 to the young product within it; while in the second, it all passes in 

 the open air, outside of the parts of the adult animal. 



§. II. Of the Allantoic. 



451. The allantois has by turns been admitted and rejected in 

 the human ovum, from the earliest history of anatomy until our own 

 times, and even now most authors agree in rejecting its existence. 

 All indeed who have described it speak of it merely from analogy, 

 or have mistaken it for an organ with which it is important that it 

 should not be confounded. 



M. Lobstein has described the umbilical vesicle itself for the 

 allantois; M. Dutrochet is still farther from the truth in taking for 

 this organ the inorganic pellicle that lines the interior of the mem- 

 biana caduca. Lacourvee, Hoboken, Diemerbroeck, Hales, Nouf- 

 ville, Littre, Rouhault, &c., affirm that they have observed it at all 

 periods of pregnancy; some have even given drawings of it; but all 

 their observations are referable to a primary error; it is the cKorion, 

 confounded anteriorly to their day with the anhistous membrane, 

 that they have described in place of the allantois. 



452. In an ovum of about twenty days old, for which I am in- 

 debted to the kindness of Dr. Terreux, the space between the amnios 

 and chorion, which was quite considerable, as it should be in the 

 first month of pregnancy, was almost entirely filled by a fungous 

 substance of a brownish yellow color, which was less thick the 

 nearer it was observed to the umbilical cord, while it was several 

 lines thick at the point diametrically opposite. Notwithstanding 

 this great thickness, it was impossible for me to divide it into several 

 laminae; it appeared to be formed of an infinite number of filaments 

 and lamellae, disposed without regular order, but so as to form a 



