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Rh previous to their union with the actual capillaries. Now it is certain that a great many stellate cells are found in the tail of the tadpole. They lie beneath the epithelium and pigment-cells on the same plane with the capillary vessels; are smaller than the pigment-cells, and contain a colourless or palish yellow substance; they send off processes on different sides, which vary in number very much in different instances, but are generally short, and for the most part do not join with processes from other cells. Their shape has no sort of connexion with that of the pigment-cells which le above them, for when, as is the case in many larvae, the latter only send off prolongations on two sides, these cells exhibit several pro- cesses on different sides. They cannot, therefore, be young pigment-cells. Such branches of the capillaries, as those at d, sometimes appear to be connected with one of those stellate cells, and the others might, therefore, be regarded as young cells of capillary vessels which had not as yet begun to anastomose. ‘These anastomoses, however, are not sufficiently evident to enable me positively to assert their existence. The great number of these stellate cells, and their presence at all ages of the tadpole, are also circumstances unfavorable to the supposition that they are primary cells of capillaries. They might, indeed, be conceived to indicate a lower stage of development, as not having yet undergone any change, and that eventually capillary vessels may be developed from some, whilst others continue their existence without such a transformation, and fill the place of cells of areolar tissue. That, however, would be somewhat too hypothetical, and I shall, therefore, not adduce these cells as proof of the existence of primary cells of capillary vessels. The uncertainty which attaches to the observations on this point in the tail of the tadpole appears, however, to be removed when we examine the incubated hen’s egg.

4, When the germinal membrane of an hen’s egg which has been subjected to thirty-six hours’ incubation (at which period the formation of red blood has commenced, and is distinctly perceptible), is placed under the microscope, and the area pellucida examined with a magnifying power of 450, the capillary vessels are readily distinguished in it by their yel-