50 ORGANISED FLUIDS. 



around them a vesicle, analogous to that which surrounds the 

 white globules. The largest remain single, but are equally 

 enveloped in a like covering. These soon break up into 

 granules, in which state the milk globules bear a close re- 

 semblance to the white globules of the blood, from which, 

 finally, they are not to be distinguished. " The blood," 

 Donne remarks, " then shows itself very rich in white glo- 

 bules ; but, little by little, these undergo modifications more 

 and more profound ; their internal molecules become effaced, 

 and dissolved in the interior of the vesicle, the globule is 

 depressed, and soon it presents a faint yellow colouration : 

 they yet resist better the action of water and acetic acid 

 than the fully formed blood globules, and it is by this that 

 they are still to be distinguished. At length, after twenty- 

 four hours, or, at latest, after forty-eight, matters have re- 

 turned to their normal state ; no more milk globules are to 

 be found in the blood, the proportion between the white 

 globules and the blood globules, between the imperfect and 

 the perfect globules, has returned to what it is ordinarily ; 

 in a word, the direct transformation of the milk globules 

 into blood globules is completed." 



In the opinion that the milk globules are convertible into 

 the white globules of the blood Donne is probably correct, 

 although it must be an inquiry of much delicacy and nicety 

 to determine this point by direct observation. The evidence, 

 however, in favour of his latter position, viz. that the white 

 globules become ultimately converted into red corpuscles, 

 is much more defective, and the facts upon which he relies 

 to sustain this view are open to question, as we have already 

 seen. 



The view, then, of the transformation of white corpuscles 

 into red, I consider to be erroneous, and that the white 

 corpuscles, as they differ from the red, in form, structure, 

 and chemical composition, so they also differ in origin ; 

 and that the two forms of corpuscles are in every respect 

 distinct, as well in function as in origin. 



From the fact of the white corpuscles of the blood being 

 encountered in considerable quantities in the lymph and chyle, 



