Inquirij into the Nature and Properties of the Blood. 4'il 



(Joes he mention the investing vesicle or the central nucleus : 

 and what is singular, he never could discover them in some 

 animals, as in the silkworm and lobster. He regards these 

 bodies as liquids possessing a central attraction, which deter- 

 mines their figure. Torre stated them to be like flattened 

 annular bodies, or like rings composed of a number of se- 

 parate parts cemented together. To Monro, they appeared 

 as circular flattened bodies like coins, with a dark spot in the 

 centre, which he conceived was owing to a depression, and 

 not to a perforation. Cavallo believes them to be simple 

 spheres. The account recently given of these bodies by Dr. 

 Young confirms in a degree the statement of Hewson. He 

 remarks, that if the globules be viewed by a strong light, they 

 will appear like simple transparent spheres ; but that if we 

 examine them by a confined and diversified light, we shall be 

 better able to ascertain their real figure and structure. The 

 red particles of the skate, as being larger and more distinct, are 

 better fitted for such an examination. These are almond-shaped, 

 and consist of an external envelope containing a central nu- 

 cleus. This central nucleus is independent of the envelope ; 

 for when this latter has been removed or destroyed, the nu- 

 cleus still appears to retain its original form *. 



With regard to the size of the red globules, there has been 

 as much diffeience of opinion as we have adduced respecting 

 their form. The medium of the most correct observations 

 and measurements would represent a globule to be about the 

 SOOOdth part of an inch in diameter. 



The external envelope, from the most recent observations, 

 is now believed to be either principally or entirely the colouring 

 matter, and the central nucleus itself to be without colour. It 

 was generally supposed that the particles were soluble in wa- 

 ter: but Dr. Young informs us, that it is the colouring matter 

 which is contained in the envelope that is so ; and he points 

 out a method by which the central nucleus may be procured, 

 retaining its perfect form in water, after the red part has been 

 dissolved. 



The information we possess of the origin of these red glo- 

 bules is extremely vague and indefinite, whilst we appear to 

 be entirely ignorant of the mode of their formation. An in- 

 teresting account is given in the Philosophical Transactions lor 

 1819, by Sir E. Home, of some observations that were niade 

 by Mr. Bauer on the serum of the blood. Mr. Bauer remarks, 

 says Sir Everard, " that the globules in the blood arc pro- 

 duced in tiie serum, I first observed in July 1817; when I ex- 



* Bostotk'b Phjsiology, vol. i. p. 157' 



amincd 



