Page:The third Huxley lecture.pdf/22

18 touch of the web the corpuscles, both red and white, moved along with the plasma with the most perfect freedom.

But I was not altogether satisfied with this evidence of their entire absence of adhesiveness within healthy vessels, because the aggregation of the red discs in the frog is of a somewhat indefinite character. I therefore sought further light upon the point in the mammalian bat. Having placed one under chloroform and extended one of its wings under the microscope, I temporarily arrested the circulation by compressing the main vessels of the limb; and on examining one of the veins I was much disappointed to see the red corpuscles of its contained blood aggregated. It seemed possible, however, that the part of the membrane which I was examining might be suffering mechanical irritation from pressure between the glass slide on which it rested and the cover-glass which it was necessary to use with the high magnifying power required for the bat's wing. For those were not the days of immersion lenses. I therefore made arrangements to guard against the possibility of such an occurrence; and now, to my great joy, I beheld the red corpuscles, which lay motionless in a considerable venous channel, distributed uniformly through the plasma, without the slightest appearance of aggregation.

The animal having been killed immediately afterwards, I examined a drop of blood from its heart. The contrast with what I had seen in the healthy