362 



THE MICROSCOPE. 



to form is in the camel-tribe, where they are oval, and resemble those 

 of the oviparous vertebrata ; those of the frog are shown in fig. 172, 

 No. 2. In the proteus, they are of a much larger size than in any 

 animal, being the l-400th of an inch in the longest diameter ; in the 

 salamander, or water-newt, 1 -600th ; in the frog, l-900th ; lizards, 

 l-1400fch; in birds, l-1700th ; and in man, the l-3200th of an inch. 

 Of fishes, the cartilaginous have the largest corpuscles ; in the gold- 

 fish, they are about the 1-1 7 00th of an inch in their longest diameter. 

 The large size of the blood-disks in reptiles, especially in the 

 JBatrachia, has been of great service to the physiologist, by enabling 

 him to ascertain many particulars regarding their structure which 

 could not have been otherwise determined with certainty. Among 



fig. 172. 



1. A portion of the web of a frog's foot, spread out and slightly magnified to show 

 the distribution of the blood-vessels. 2. A portion of same highly magnified, 

 showing the ovid form of the blood disks in the vessel, beneath which a layer of 

 hexagonal nucleated epithelium-cells appear. 3. Human blood-disks, magnified 

 200 diameters, as they appear when fresh drawn. 



other facilities which this occasions, is that of procuring their separa- 

 tion 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 fluid part of the blood has flowed through, 



A new and very interesting subject has lately been noticed the 

 production from the blood, under certain circumstances, of red albumi- 



