72 OHGANISED FLUIDS. 



viewed thus for hours, during the whole of which time the 

 blood will be seen flowing on with undiminished force. In 

 certain vessels, however, after a very long exposure of the 

 tongue to the action of the air, whereby its moisture is con- 

 tinually abstracted, and which acts, doubtless, as a source of 

 irritation, a number of the colourless globules will be seen to 

 have collected in the capillaries ; these adhere principally to 

 the sides of the vessels and to each other, thus leaving the 

 channel still free for the passage of the red globules, which 

 in their course sometimes rush against the white globules 

 with such violence as to detach one or more of them from 

 time to time from its adhesion to the walls of the vessel, and 

 which, rolling over once or twice, joins the general current of 

 the vessel, and is quickly carried out of view. It would 

 appear that any irritation affecting the capillary vessels, 

 even when applied to them outwardly, as, for example, weak 

 chemical solutions, gives rise to the phenomenon in question. 

 It is to be observed, however, that at all times considerable 

 numbers of white corpuscles circulate in the larger capil- 

 laries: these do not occur mixed up with the red blood 

 corpuscles ; but, as already remarked, are situated externally 

 between them and the inner wall of the capillaries. (See 

 Plate V.jg. 1.) 



In the plastic power with which the red corpuscles are 

 endowed, we recognise a beautiful and important organic 

 adaptation of matter to the fulfilment of a special purpose. 

 Were it not for this plastic property, and were the red cor- 

 puscles of the blood, on the contrary, of a solid and unyield- 

 ing texture, it would follow, as an inevitable consequence of 

 the solidity of the globules, combined with their vast number, 

 that frequent interruption and stoppage of the circulation in 

 the capillaries would ensue, and which would, of course, 

 result in the complete derangement of the functions of the 

 entire economy. 



I come now to record an observation which, so far as I am 

 informed, is without parallel. On one occasion, in examining 

 the tongue of a frog a portion of it broke away from the 

 remainder ; this I placed between two plates of glass, and 



