220 THE FOETUS. 



placenta, through simple pores, by a sort of imbibition which might 

 be explained by a mere contiguity of surfaces. To this I can only 

 object, that the blood, as such, does not appear to pass in any way 

 into the ovum. It certainly does not pass there at least in the early 

 periods; for the villous portions of the chorion do not contain ves- 

 sels until pretty late, and besides, its filaments are never hollow quite 

 to their extremities (475). On the other hand, both Autenreith's 

 and my own experiments demonstrate that the blood of the foetus 

 does not present the same aspect as that of the mother: it is at 

 first of a rose color: it then becomes redder, then blacker, and 

 does not exhibit any difference of color in the veins and arteries. 

 Tiedemann and others have found that it contains a much larger 

 proportion of serum than the blood of an adult, and is less coagulable; 

 in fine, every thing proves that its chemical composition is very dif- 

 ferent from that of the mother. Even although chemistry had not 

 been able to ascertain for us these differences, would it be right to 

 believe that this fluid need not have, like our aliment, a due relation 

 to the period of our life, whether extra or intra-uterine, and that the 

 blood of an adult woman would not be, in some sort, a poison to so 

 frail and delicate a being as the embryo, or foetus ? Were it worth 

 ■whi'e to insist upon this point, I might add that according to the 

 microscopical observations of MM. Prevost and Dnmas, the blood- 

 globules are so small in the foetus, that it would be impossible for 

 those of the mother to pass through the same canals or same orifices 

 without destroying the equilibrium of all the functions, and producing 

 sudden death. 



If, therefore, the blood is poured into the caverns of the placenta, 

 or taken up by the pores of that organ, it must at least undergo 

 some elaboration, some important modification before it reaches the 

 umbilical vein; but what is the nature of that modification? I know 

 not. 



566. In conclusion, the nourishment of the ovum is dependent on 

 various sources; at first it is a mere vegetable, which imbibes the sur- 

 rounding moisture. The villi of its superficies, real cellular spon- 

 gioles, acquire, in the tube or in the womb, the nutritive principles 

 required for the development of the embryo vesicles; after which the 

 embryo is nourished after the manner of the chick in ovo, or rather 

 like the young plant, which is at first evolved at the expense of prin- 

 ciples contained in its cotyledons. It gradually exhausts the vitel- 

 line matter contained in the umbilical vesicle; the emulsive substance 

 of the reticulated body or allantois is also gradually absorbed. It 

 reaches the end of the second month; the vessels of the cord are 

 formed; the placenta soon begins to show itself, and suffices to keep 



