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or Red Disks of the Mammiferous Animals. 25 



in the relative exactness of the instrnment I am disposed from 

 long experience to put much confidence, which is of the 

 greatest importance where the results are to be obtained 

 chiefly by comparisons. 



The corpuscles were examined thinly spread on glass and 

 quickly dried, also floating in their own serum, and diluted 

 when necessary with weak saline solutions, or sugar and water, 

 or with urine. The objection to these substances is, that they 

 all more or less alter the figure of the globules, generally ren- 

 dering many of them cup-shaped and diminishing their size 

 slightly. Indeed, the disks kept in their own serum often ap- 

 pear a little smaller in a very short time after they have been 

 removed from the vessels, as if they possessed some degree of 

 contractility. It might be supposed that the particles rapidly 

 dried on glass would shrink a little; but this is not the case, 

 for they retain a remarkably clear and regular outline, and 

 are commonly, to a small extent, larger than those of the same 

 blood exposed to the air in their own fluid. 



In some instances there was certainly a slight enlargement 

 in the dried corpuscles, as compared with those seen in their 

 own serum immediately after they were taken from the ani- 

 mal. In the greater number of trials, however, the sizes of 

 the wet and dry disks corresponded accurately. In most cases s/^ 

 the measurements were repeated by Mr. Siddall, an experi- ' 

 enced micrographer, with another instrument by Ross, so as to 

 avoid as much as possible accidental inaccuracies. The mea- 

 surements are always expressed in fractions of an English inch. 

 As the corpuscles are very liable to change in size and form 

 from very trivial causes, the extreme measurements in no case 

 include those large or small particles which occur but spa- 

 ringly, and which, perhaps, are not identical with the common 

 red disks. Neither the large white globules nor the granu- 

 lated particles are estimated, because, independently of their 

 spherical shape, the former are almost uniformly larger and 

 the latter smaller than the blood disks. As noticed by Hew- 

 son, the common corpuscles become mulberry-shaped when, 

 from incipient putrefaction, their colouring matter begins to 

 dissolve in the serum. But 1 have observed the granulated 

 particles in great numbers, both in their serum and in the 

 dry state*, in blood examined immediately after it was ob- 

 tained from the veins of various animals, particularly young 

 kittens. The nature of these particles is worthy of further 

 and special inquiry. They are to be found plentifully during 



* I gave Mr. Owen specimens of these granules in September last, men- 

 tioning this fact to him, as he considered the granulated appearance to be 

 the effect merely of drying. 



