punctum saliens when all but dead, and no longer giving any signs of motion, recover its pulsatile movements under the in- fluence of renewed warmth. In the order of generation, then, I conceive that the punctum and the blood first exist, and that pulsation only occurs subsequently.
This at all events is certain, that nothing whatever of the future foetus is apparent on this day, save and except certain sanguineous lines, the punctum saliens, and those veins that all present themselves as emanating from a single trunk, (as this itself proceeds from the punctum saliens,) and are distributed in numerous branches over the whole of the colliquament or dis- solved fluid. These vessels afterwards constitute the umbilical vessels, by means of which, distributed far and wide, the foetus as it grows obtains its nourishment from the albumen and vi- tellus. You have a striking example of similar vessels and their branchings in the leaves of trees, the whole of the veins of which arise from the peduncle or foot-stalk, and from a single trunk are distributed to the rest of the leaf.
The entire including membrane of the colliquament traversed by blood-vessels, corresponds in form and dimensions with the two wings of a moth; and this, in fact, is the membrane which Aristotle 1 describes as "possessing sanguineous fibres, and at the same time containing a limpid fluid, proceeding from those mouths of the veins/'
Towards the end of the fourth day, and the beginning of the fifth, the blood-red point, increased into a small and most deli- cate vesicle, is perceived to contain blood in its interior, which it propels by its contractions, and receives anew during its diastoles.
Up to this point I have not been able to perceive any differ- ence in the vessels : the arteries are not distinguished from the veins, either by their coats or their pulsations. I am therefore of opinion, that all the vessels may be spoken of indifferently under the name of veins, or, adopting Aristotle's 2 term, of venous canals.
" The punctum saliens," says Aristotle, " is already possessed of spontaneous motion, like an animal." Because an animal is distinguished from that which is none, by the possession of
1 Loc. supra cit. * Ib.
