THE BLOOD. 27 



the fibrin of the blood is abstracted, they do not thus cohere. 

 Professor Nasse, as already remarked, states that this dispo- 

 sition on the part of the red corpuscles to unite together and 

 form rolls (as of miniature money in appearance), is increased 

 in inflammatory blood. The union does not, however, last 

 long ; a heaving to and fro of the strings of corpuscles soon 

 taking place, and which terminates in their disruption.* 



Size. The size of the red corpuscles of the blood, although 

 more uniform than that of the white, is nevertheless subject 

 to considerable variation. Thus, the globules contained in 

 a single drop of blood are not all of the same dimensions, 

 but vary much. These variations are, however, confined 

 within certain limits : the usual measurement in the human 

 subject is estimated at about the ^j^o ^ an i ncn ; but, 

 occasionally, globules are met with not exceeding the 4/45 '> 

 and, again, others are encountered of the magnitude of the 

 75 2T-g f an i 110 * 1 : th ese are ? however, the extreme sizes 

 which present themselves. f The difference in the size of the 



* In reptiles, birds, and fishes, the red globules are elliptical, a form 

 possessed also by some few mammalia, chiefly of the family Camelidce. 

 This fact was first discovered by Mandl, in the dromedary and paco ; and 

 subsequently by Gulliver, in the vicugna and llama. The oval globules 

 of these animals, however, could not be confounded with those of reptiles, 

 birds, and fishes, than the corpuscles of which they are so much smaller, 

 and, further, are destitute of the central nucleus, which characterises the 

 blood globules of all the vertebrata, the mammalia alone excepted. The 

 long diameter of the blood corpuscles of the dromedary, Mr. Gulliver 

 states to be the -g^V^ of an inch, and its short the ^-g^-j- ; the first of these 

 measurements exceeds but little the diameter of the human blood cor- 

 puscles. 



Amongst fishes one exception to the usual oval form of the blood 

 corpuscle has been met with: this occurs in the lamprey, the blood disc of 

 which Professor Rudolph Wagner observed to be circular ; in form then 

 the blood corpuscle of the lamprey agrees with that of the mammalia, but 

 in the presence of a nucleus, the existence of which has been recently 

 ascertained by Mr. T. W. Jones, it corresponds with the structure of the 

 blood discs of other fishes. 



t The first measurement given is that which is usually adopted by 

 writers ; the last two are those made by Mr. Bowerbank for Mr. Owen, 

 and which are to be found in the latter gentleman's paper on the Com- 

 parative Anatomy of the Blood Discs, inserted in the Lond. Mod. Gazette 



