222 RED PARTICLES 



and so on, gradually increasing the quantity ; and in proportion 

 as water is added, the figure of the particle will be changed 

 from a flat to a spherical shape. When much water is added, 

 the vesicle will by degrees become thinner and more transpa- 

 rent, and will at last be dissolved. When the vesicle has thus 

 assumed a spherical shape, it will roll down the glass stage 

 smoothly, without those phases which it had when turning over 

 whilst it was flat ; and as it now rolls in its spherical shape, 

 the solid middle particle can be distinctly seen to fall from side 

 to side in the hollow vesicle, like a pea in a bladder. Some- 

 times, indeed, instead of falling from side to side, the solid 

 middle particle is seen to stick to one part of the vesicle ; and 

 in proportion as the vesicle, instead of being flat, assumes a 

 spherical shape, its longest diameter is shortened, as might be 

 expected on the supposition of its being hollow and flat (en). 



(en.) The figures of Leeuwenhoek* indicate the nucleus in the cor- 

 puscles of the salmon and flounder. Bidloo b called the corpuscles 

 globosee vesiculse. Emanuel Weis c inferred that the circumference 

 both of the oval and round corpuscles must be bounded by a membrane ; 

 and he speaks of the nucleus as a distinct part. Hewsou's demonstra- 

 tion of the nucleus and envelope in the corpuscle of the lower vertebrata 

 is good ; but I believe he erred in stating that a similar nucleus exists 

 in the human blood-corpuscle. 



The majority of the red corpuscles in man, and other mammalia, after 

 an early stage of intra-uterine life, have no nucleus corresponding to 

 that so obvious in the corpuscles of the lower vertebrate animals ; d and 

 even the oval corpuscles of the camelidse agree with the corpuscles of 

 other mammals in this respect. But in the very young embryo of mam- 

 mals the blood-corpuscle has a distinct nucleus, the true representative 

 of the permanent nucleus in the corpuscle of lower animals ; and the 

 blood of such embryos at the earliest period is pale, from an abundance 

 of free globules like the nuclei, as noticed in Dr. Carpenter's Report, 

 ' British and Foreign Medical Review/ vol. xv, p. 273. 



Professor Owen e is surprised that Messrs. Delpech and Coste were 

 ignorant of Mr. Hunter's claim to the discovery that it is a pale or 

 colourless blood that first circulates in the embryo of a red-blooded 

 animal. Yet this discovery was certainly made as early as 1654, for 

 Glisson f knew of it ; so did Needham, g and some of his successors in 

 the first half of the last century. 



When the blood-corpuscle of mammalia is deprived of its colouring 



* Select Works, tr. by Sam. Hoole, vol. d See Notes cxxxvn and cxxxix. 



ii, pi. 17, fig. 26-8. 4to, Lond. 1807. e Hunter's Works, vol. iv, p. xiii, 8vo, 

 b Anatomia Human! Corporis, tab. xxiii, Lond. 1837. 



f. 16, Fol. Ams. 1685. f Anat. Hepat. p: 411, 8vo, Lond. 1654. 



c Acta Helvetica, torn, iv, pp. 355-56, De Formato Fcetu, pp. 72-3, 12mo, 



4to, Basiliae, 1760 ; torn, v, 1762. Lond. 1667. 



p. 348. 



