550 THE MICROSCOPE. 



the Musk-deer, in which the corpuscles are of extreme 

 smallness, about the 1-1 2,000th of an inch in diameter. 

 The Elephant has the largest, which are about the 1 -2,000th 

 of an inch in diameter. The Goat, of all common animals, 

 has very small corpuscles ; but they are, withal, twice as 

 large as those of the Musk-deer. Another exception in 

 regard to form is in the Camel-tribe, where they are 

 oval, and resemble those of the oviparous Vertebrata, 

 as the Frog, shown in fig. 285, 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, l-600th; in the Frog, l-900th; 

 Lizards, l-l,400th; in Birds, l-l,700th; and in Man, the 

 1-3, 200th of an inch. Of Fishes, the cartilaginous have 

 the largest corpuscles ; in the Gold-fish, they are about the 

 1-1, 700th of an inch in^ their longest diameter. 



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

 in the Batrackia, has been of great service to the physio- 

 logist, by enabling him to ascertain many particulars 

 regarding their structure which could not have been 

 otherwise determined with certainty. Among other facili- 

 ties 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 filter- 

 ing-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 no- 

 ticed the production from the blood, under certain condi- 

 tions, of red albuminous crystals, which, although formed 

 from animal matter, and sometimes, in all probability, 

 during life, have the same regular forms as inorganic crys- 

 tals. Virchow was the first who paid particular attention to 

 their actual nature, and proved them to differ from saline 

 or earthy crystals. If we add water to a drop of blood 

 spread out under the object-glass of the microscope, as the 

 drop is beginning to dry up, the edges of the heaps of blood 

 corpuscles are seen to undergo a sudden change: a few 

 corpuscles disappear, others have dark thick edges, become 

 angular and elongated, and are extended into small well- 

 defined rodlets. In this manner an enormous quantity of 

 crystals are formed, which are too small to enable us to 



