172 LECTURE VII. 



by the action of chemical fluids, certain quantities of 

 water are abstracted from the corpuscles, and that they 

 then shrivel up and experience peculiar changes in form, 

 which might very easily give rise to errors. These are 

 not unimportant conditions, and I will therefore now add 

 a few words concerning them. 



When a blood-corpuscle is exposed to a loss of watei 

 by the action of a strongly concentrated liquid upon it, 

 the first thing we observe is that, as fast as fluid exudes, 

 little prominences arise on the surface of the corpuscle, 

 at first very much scattered, sometimes at the border, 

 sometimes more towards the middle, and in the latter 

 case, occasionally bearing a deceptive resemblance to a 

 nucleus (Fig. 52, e,f). This has been the source of the 

 erroneous assumption of nuclei, which have been so 

 much described. If a blood-corpuscle be watched for a 

 considerable time whilst under the action of concentrated 

 media, more and more protuberances are seen to arise, 

 and the surface of the corpuscle becomes less in diameter. 

 At the same time, little folds and knobs form with con- 

 tinually increasing distinctness on the surface, and the 

 cell becomes jagged, stellate, and angular (Fig. 52, g). 

 Jagged bodies of this sort are to be seen every moment 

 on examining blood which has been for some time ex- 

 posed to the air. Even mere evaporation will produce 

 this change. We can effect it with great rapidity by 

 altering the composition of the serum by the addition of 

 salt or sugar. If the abstraction of water continue, the 

 corpuscle grows smaller still, and ultimately becomes 

 smooth again, and at the same time globular (Fig. 52, h), 

 or even perfectly spherical, whilst its colour appears 

 much more intense, and the contained mass assumes 

 quite a deep blackish-red hue. Hence we are able to 

 draw the not uninteresting conclusion, that this exos- 

 mosis consists essentially in a withdrawal of water, dur- 



