OF THE BLOOD. 229 



If, then, they really be not globular, but flat, and if water- 

 so readily alters their shape, whence is it that the serum has 

 the property of preserving them in that form, which seems so 

 necessary ? because it is so general through the animal creation. 



It is principally by the salts of the serum that this effect is 

 produced, as is proved by adding a small quantity of any neutral 

 salt to water, when the water is no longer capable of dissolving 

 those particles, nor does it alter their shape when the salt is 

 used in a certain proportion. 



EXPERIMENT III. 



If a saturated solution of any of the common neutral salts 

 be mixed with fresh blood, and the globules (as they have been 

 called, but which, for the future, I shall call flat vesicles) be 

 then examined* in a microscope, the salt will be found to have 

 contracted or shrivelled the vesicles, so that they appear quite 

 solid, the vesicular substance being closely applied all round 

 the central piece. In proportion as the solution of salt is diluted 

 with water, it has less effect, and when diluted with six, eight, 

 ten, or twelve times its quantity of water, it produces no change 

 in the figure of the vesicles, whose flat shape can then be seen, 

 even more distinctlv than when mixed with serum itself fcxi). 



flexible, changing their form in passing a narrow channel, and re- 

 assuining their usual contour when they come into a larger space. In 

 mammalia, indeed, the corpuscles are very soft and elastic; when 

 passing a narrow capillary vessel, or impinging on a grosser particle, 

 they may be seen to become suddenly elongated, twisted, bent, or in- 

 dented ; deeply 'concavo-convex ; comma-shaped or spindle-shaped, a 

 part of the corpuscle being drawn into a thread ; and after all these 

 rapid changes, the corpuscles as quickly recover their original form. 

 The cup-shaped variety is often seen in blood on the object-plate of the 

 microscope. See the English edition of Gerber's 'Anatomy,' Note, 

 p. 79, and Appendix, pp. 11, 12; and * London and Edinburgh 

 Philosophical Magazine,' November, 1840, p. 329, for a figure of more 

 permanent forms, chiefly spear-shaped, lunated, and sigmoidal, which 

 the majority of the corpuscles of some mammalia, from an unknown 

 cause, occasionally assume. 



(cxi.) When a solution of salt is added to the blood, the corpuscles 

 are made very distinct, for they are separated from each other, and their 

 adhesiveness is quite destroyed : see Notes xxm and c. They become 

 smaller ; some preserve their form, but the majority are less regularly 

 circular, being bent, indented, or cup-shaped ; many exhibit oblong, 



