FORMATION OF THE RED PARTICLES. 275 



solution of any neutral salt be added to this mixture before 

 the bursting of the vesicle, it immediately becomes flattened, 

 and the particle of blood reassumes its original figure. In 

 the natural state of a particle of blood, the vesicle is collapsed, 

 and is in contact with, or adheres to, the central particle so 

 firmly as to retain the particle in the middle of it ; but when 

 water is added to the blood, and the vesicle becomes a sphere, 

 that union is broken, the central particle becomes loose in 

 the vesicle, and then only its motion can be distinguished 

 (cxxxvn). 



SECT. 80. The figure and size of the particles of the blood 

 differ in different animals (cxxxvin) ; but the general con- 

 formation of vesicle and particle extends probably throughout 

 animal nature (cxxxix). That particles thus formed should 

 not be made by the mere agitation of the chyle in the lungs 

 seems probable ; that they are not, it shall be our business to 

 prove, and also that the lymphatic system and its appendages 

 are the organs employed by nature to do this office. By the 

 lymphatic system and its appendages we mean the lymphatic 

 vessels, the lymphatic glands, the thymus, and the spleen. 



SECT. 81. At the first view it may seem extraordinary that 

 nature should have given so many and so complicated organs 

 to form a part only of the blood, when she effects other secre- 

 tions by organs apparently more simple ; but our surprise must 

 cease when we reflect, that upon a due formation of these par- 

 ticles, not only the various functions of the body, but also the 

 very existence of the animal, in a great measure, depends. 

 When we consider how liable these parts are to disease, by 

 which their offices would be impeded, we must necessarily 

 admire the goodness of the Author of our nature for so form- 



(cxxxvu.) This description of the nucleus is evidently taken from 

 the blood-corpuscles of an oviparous vertebrate animal, and is not 

 applicable to those of mammalia. In short, the nucleus is a perma- 

 nent part of the red blood-corpuscle of oviparous vertebrata, and 

 only a temporary part of the red blood-corpuscle of mammalia: see 

 Note cii, pp. 222-3. 



(cxxxvm.) See the Tables of Measurements, Note cxvin*, 

 pp. 237 et seq. 



(cxxxix.) In mammals the nucleus of the red blood-corpuscle soon 

 disappears : see Notes en and cxxxvu. 



