68 ORGANISED FLUIDS. 



clearness to enable the observer to pronounce with confidence 

 upon its presence. After the lapse of a few minutes it becomes 

 much more apparent, so that its composition is easily to be 

 discerned : this arises, most probably, from the discharge of a 

 portion of the colouring matter of each globule. The form 

 of the nucleus is seen to correspond with that of the blood 

 corpuscle itself, and to be oval, presenting a granular struc- 

 ture precisely resembling that of the white globules of the 

 blood, from one of which it is only to be distinguished by its 

 much smaller size and oval form. (See Plate YL.Jlg. 2.) 



Owing to the firmer texture and greater size of the blood 

 globules of the frog, their structure can be well studied, and 

 the effects of re-agents more easily determined. 



In water, the red corpuscles lose their colour, and become 

 circular, and indeed globular, a change of form which the nu- 

 cleus is likewise seen to undergo. (See Plate TL.Jigs. 3 & 4.) 

 These alterations ensue almost immediately on the application 

 of the water: its continued action produces an effect still 

 more remarkable ; the nucleus, which at first occupied a central 

 position in the globule, is soon seen to become excentric, and 

 finally, rupturing the pseudo -membrane of the corpuscle, 

 escapes into the surrounding medium ; the nucleus and the 

 outer portion of each globule are then observed as two distinct 

 structures, lying side by side (see Plate II. Jig. 4.) ; the 

 latter is at length absorbed, and then nought remains but the 

 nucleus, which is, as already remarked, under the influence of 

 water rendered of a globular form, and which is in no way 

 distinguishable from a white corpuscle of the blood, save in 

 the single particular of size, the nucleus being several times 

 smaller than the globule. 



Acetic acid dissolves, if strong almost immediately, the 

 outer tunic, without occasioning the prior extrusion of the 

 nucleus, the form of which is not materially affected, the con- 

 tained granules merely becoming more clearly defined. (See 

 Plate II. Jig. 5.) 



The white globules in the blood of the frog are very 

 numerous ; they bear no similitude of form or size to the 

 elliptical red blood corpuscles, being usually perfectly sphe- 



