the same way. Now you have circulation but it is not yet blood nor are these channels closed. They Christian Louboutin Outlet are simple furrows in the substance of the yolk. As yet it is only yolk flowing through yolk though the flowing yolk is somewhat different in appearance from that which surrounds it and which afterward builds up the walls of the vessels. Meanwhile the walls of the longitudinal furrow formed by the rising ridges along the middle line of the germ meet and unite thus transforming the open furrow into a close cavity. One end of this cavity becomes somewhat wider then the rest and has lateral undulations. Within this portion of the cavity is hereafter to be the head.At some future time long after the period I now describe there will be not only a hrain forming in this front cavity but alsoall those parts which constitute the head and connect with the spinal-marrow which is enclosed in the straight and narrow part of the cavity. The lower edge of the embryonic disc goes on increasing extending gradually downward over the yolk until it has taken in the whole mass closing over it so as to form the walls of another cavity below; this cavity though it is now full of yolk and contains nothing else will in the course of time be transformed by a series of changes into a mouth lungs chest abdomen Coach Outlet Store Online in short all those organs of respiration digestion etc by which life is maintained. But as yet I repeat it is nothing but a bag full of yolk enclosed in a bag of yolk-cells which have undergone certain slight changes from their primitive character. The upper cavity is nothing but a channel formed by the ridges on the surface of the germ which have become united along the middle line. Coach Outlet Store Online The channels of moving yolk arising from a pool here Nike Shoes Australia and there are only gradual depressions in the yolk-mass slowly covering or enclosing themselves with yolk-cells or with a yolk of a peculiar kind which forms walls around them. Suppose that water flowing through a rut on the ground after a heavy rain should line the walls of that rut with mud so as to consolidate the rut and that with heavy rain this process should go on always increasing and strengthening the consolidation you would then have a process resembling that through Christian Louboutin Outlet which these channels of fluid yolk are transformed into vessels into closed tubes circumscribed by the coherence of minute particles of the fluid itself which j adheres to the sides of the channels and changes what were at first mere ruts into the closed cylinders aqueducts or ducts which we call Nike Air Max blood-vessels. The chick has now a heart and that heart begins to contract to heave and fall so that the fluid within is pressed out Nike Air Max 90 and a relation begins between the heart and the channels outside. Through these channels which are still open a certain amount of yolk is constantly moving and falling into the current and it is this yolk which is transformed into blood. This process goes on so rapidly that by the time the parts have reached the phase in which I have described Nike Australia them the fluid is tinted with reddish blood-corpuscles. These blood-discs are only modified yolk-cells. They have not the character of perfect blood; they have not all the characteristics of that blood which we make from our food when it passes through the vessels into the respiratory organs and is there transformed into regular blood-discs. In all this we have nothing I repeat bnt the transformation of yolk through its own agency into a variety of substances derived from the yolk itself and so distributed and differentiated as to build up a frame having all the properties of the parent animal from which the yolk is derived.Here is something wonderful! Not only the simplicity of the process by which these changes are brought about attracts our notice but still more marvellous is the fact that all this goes on from within. There is a principle acting by the aid of the substance which holds it never deviating from its course and always leading to the reproduction of Coach Outlet Store Online a being like the parent. How that influence from the parent is