78 ORGANISED FLUIDS. 



but to differ from that of the Oviparous Vertebrata in not 

 being developed around a central nucleus. 



DISSOLUTION OF BLOOD CORPUSCLES. 



But if the blood of the embryo fowl is well adapted for the 

 study of the origin and development of red blood corpuscles, 

 that of the adult fowl is no less fitted for ascertaining their 

 end and final destination. 



Some observers have entertained the idea, already ex- 

 pressed in this work, that the older blood discs become melted 

 down in the liquor sanguinis, and thus, by their dissolution, 

 increasing the amount of fibrin held dissolved in that liquid. 

 To the adoption of this notion they were driven because 

 they were unable to dispose of the red blood disc in any 

 other way, and which other facts had made apparent to them 

 could not be regarded as persistent structures. 



In proof of the accuracy of this statement respecting the 

 melting down of the corpuscles, they had not, however, a 

 particle of direct evidence to adduce. I will now proceed 

 to show that the view referred to may be substantiated by 

 positive observation. 



In almost every drop of the blood of an adult fowl a 

 number of certain pale and usually colourless corpuscles will 

 be seen, having a nucleus of the same size and structure as 

 that of the ordinary red blood disc distinctly visible in the 

 midst, the investing portion of each corpuscle at the same 

 time being invariably smooth and destitute of granules. 



These corpuscles vary in size, in form, and in colour ; the 

 larger ones, which are equal in dimensions to the fully deve- 

 loped blood discs, usually retain a faint coloration, and are 

 invariably of an oval form, while the smaller ones, many of 

 which consist of merely a nucleus and a closely fitting- 

 envelope, are perfectly colourless, and for the most part, 

 although not always, spherical. (See Plate IX. Jig. 3.) 



Now there is no difficulty whatever in detecting these pale 

 and mostly spherical corpuscles with a good instrument, nor 



