430 OF NUTRITION. 



discs is about l-2745th of an inch), and the Rhinoceros (in which they are about l-3765th), 

 may be stated at about l-4200th; and there is les* variation than might have been ex- 

 pected, from the different size and conformation of the several species examined. Among 

 the Ruminantia, the corpuscles are for the most part smaller than in other orders; and 

 there is more relation between their diameter and the size of the animal, than is else- 

 where observable. Excluding the Camelidae (which are zoologically intermediate 

 between the Ruminantia and Pachydermata), we find a range of sizes extending from the 

 l-3777th to the l-12325th of an inch; the former is the diameter in one of the larger 

 Deer: the latter in the Musk Deer, which is the smallest of the whole order. In the 

 Camel tribe, the average of the long diameter of the oval corpuscles is l-3400th of an 

 inch: whilst that of the short diameter is l-6300th; and this is no where widely departed 

 from: the length of the discs is, therefore, not quite twice their breadth. Among the 

 Rodentia, the discs are rather large, especially considering the small size of most of the 

 species. In the Capybara, which is the largest animal of the order, they average l-3216ih ; 

 and in the Mouse family (the smallest of Mammalia) they are as much as l-3800th. In 

 the Squirrels, the diameter is rather less; but in scarcely any of the whole order is it 

 under l-4000th. Among the Edentata, the only species yet examined, is one of the Arma- 

 dillos, in which the diameter of the corpuscles is about the same as in the Quadrumana. 

 In the Marsupialia the range is nearly the same as among the Rodentia. 



b. In BIRDS, according to the observations of Mr. Gulliver, the long and short diameters 

 of the corpuscles usually bear to each other the proportion of 1 or 2, to 1 ; and this is 

 the general relation among Oviparous Vertebrata, with the exception of some of the 

 Crocodile tribe, in which the length is sometimes three times the breadth. The size of 

 the corpuscles of Birds has generally more relation to that of the species, than in Mam- 

 malia. No instance has yet been detected, of the occurrence of comparatively small 

 corpuscles in the larger species, and of large corpuscles among smaller animals, which 

 has been seen to be common among the former class; the blood of the Humming-birds, 

 however, has not yet been examined. The largest discs are found among the Cursores ; 

 those of the Ostrich have an average long diameter of l-1649th of an inch, and a short 

 diameter of l-3000th ; and among the larger Raptures, Grallatores, and Natatores, the 

 dimensions are but little inferior. The least dimensions hitherto observed are among the 

 small Passerine birds; in which the corpuscles have a long diameter of about l-2400th 

 of an inch, and a transverse diameter of from l-3800th to l-4800th. Circular discs may 

 be occasionally observed in some species, agreeing with the others in every particular 

 but their form; and every gradation may be noticed between these and the regular oval 

 corpuscles. 



c. The large size of the blood-discs in REPTILES, especially in Batrachia, and above 

 all, in the Perennibranchiate species of the latter, has been of great service to the Phy- 

 siologist; by enabling him to ascertain many particulars regarding their structure, 

 which could not have been otherwise determined with certainty. Among other facilities 

 which this occasions, is that of procuring their separation from the other constituents of 

 the blood ; for they are too large to pass through the pores of ordinary filtering-paper, 

 and are therefore retained upon it, after the liquor sanguinis has flowed through. The 

 blood-discs of the warm-blooded Vertebrata cannot be thus separated. The oval cor- 

 puscles of the Frog have a long diameter of about l-1000th, and a transverse diameter 

 of about l-lSOOth^of an inch; those of the Salamander or Water-newt, are rather smaller. 

 The long diameter of the corpuscles of the Proteus is staled by Wagner at l-337th of an 

 inch ; that of the Siren is about l-435th, the short diameter being about 1-SOOth of an 

 inch; the extremes of variation, however, are very wide. The long diameter of the 

 nuclei is about l-1000th or l-l 100th, and the short diameter about l-2000th; hence it is 

 about three times as long, and nearly twice as broad, as the entire Human blood-disc, 

 thus having six times its superficies; its thickness is about l-3800th of an inch. 



573. In regard to the Chemical constitution of red Blood-corpuscles, it is 

 difficult to speak with defmiteness ; since there are three parts in each disc 

 which are essentially different in character, and which may have a very dif- 

 ferent composition. These parts, the capsule, the nucleus, and the con- 

 tained matter, cannot be separated without the use of chemical reagents, which 

 must alter their respective properties. Two proximate principles have been 

 obtained from the blood-discs : these are designated as hssmatosine and globu- 

 line. To the h&matosin the red colour of the blood is due, although it con- 

 stitutes not more than a 20th or 25th part of the whole mass of dried globules. 

 When separated from the globulin, it is of a dark-brown hue, and is tasteless 

 and insoluble in water, alcohol, and ether ; but is readily soluble in water or 



