UMBILICAL VESICLE. 171 



the superior mesenteric vein and artery; I have always remarked 

 that they join one of the branches of the second or third order of these 

 great vessels, particularly those that proceed to be distributed to 

 the caecum. I have often traced them in the abdomen, through 

 the umbilical ring, and as far as one, two, and even three inches 

 along the cord, in products of six weeks, and two or three months 

 old. But they disappear at these different periods, and at last are 

 lost in the spongy tissue of the umbilical cord, before arriving at the 

 vesicle. I have several times succeeded in injecting them, and then 

 they appeared of the size of a large hair; in general, however, they 

 are so fine, that they are easily broken if sought for without the 

 greatest care. 



449. Inasmuch as I have seen them in an ovule at the same time 

 with the pedicle of the vitelline sac, from which they were perfectly 

 distinct, it appears to me they should henceforth be considered as 

 destined to carry to and take up from the parietes of the vesicle and 

 its canal, the materials that serve for the nutrition of this curious ap- 

 paratus; and not for the transfer of the vitelline substance into the 

 general circulation. 



Many reasons drawn from analogy, have led to a comparison be- 

 tween the vitelline matter and the yelks or vitelline substance of 

 the eggs of birds. In the largest umbilical vessel I ever saw, and 

 perhaps the only one where there was no possibility of this sub- 

 stance having undergone any change whatever, it was of a very de- 

 cided pale yellow, consequently opake, of the consistency of a pret- 

 ty thick emulsion, and different in all respects from serum or any 

 other known fluid of the economy. In others I have found it more 

 fluid and clearer, and in others yellower and thicker; in several spe- 

 cimens it consisted of one or two small concrete clots, resembling in 

 a remarkable manner the yelk of egg cooked and floating in a 

 slightly colored fluid; to conclude, its color is analogous to that 

 exhibited by the parietes of the vesicle itself, after the sixth week 

 of its growth. We ought, consequently, to admit, that it is a 

 nutritious substance, a sort of oil in a great degree similar to that 

 which constitutes the vitelline fluid of the hen's egg. 



450. The uses of this apparatus then are evidently connected 

 with the nutrition of the primary lineaments of the foetus; it fur- 

 nishes to the embryo its means of growth, until the cord and um- 

 bilical vessels are formed, or rather until the ovule becomes exactly 

 applied to the inner surface of the womb; numerous materials then 

 pass from the parts of the woman to those of the ovum, and the 

 umbilical vesicle soon beco.mes useless. Under this view, the appa- 

 ratus I am speaking of can be but temporary, and created to the 



