52
this behaviour of horse's blood implies, as we have seen, a high degree of adhesiveness of the red discs.
If we compare this with the perfect absence of grouping of the red corpuscles which was observed within a vein of the bat's wing, in spite of their extreme adhesiveness in the same animal in blood shed from the body, we cannot but be greatly struck with the contrast. As regards the circumstances of the two vessels, we see that in the bat's wing the vein was of small calibre, and was in its natural relations to surrounding structures; whereas the horse's jugular was of very large dimensions and isolated from the rest of the body.
It seems impossible that the adhesiveness of the corpuscles in the jugular vein was the result of isolation of the vessel from other structures. For adhesiveness of corpuscles is not occasioned in the frog's web by amputation of the limb; nor is it produced in the human subject by complete detachment of a portion of tissue; as is clearly shown by the persistent healthiness of a piece of skin entirely transplanted in skin-grafting. We are therefore forced to the conclusion that the adhesiveness of the red discs in the horse's jugular, as contrasted with its complete absence in the vein of the bat's wing, was due to the larger size of the vessel in the former case. And the only way in which it seems possible to interpret this difference of behaviour of the corpuscles in the two cases is to
