20 THE BLOOD. 



the oval, raiy in different instances, so that in some osseous fishes the 

 elliptical form is almost shortened into a circle. The blood-corpuscles 

 of invertebrata, although they (except in some of the redt-blooded 

 annelides) want the red colour, are also, for the most part, flatened or 

 disk-shaped ; being in some cases circular, in others oblong, as in the 

 larvae of aquatic insec ts. Sometimes they appear granulated on the 

 surface like a raspberry, but this is probably due to some alteration 

 occurring in them. 



The size of the corpuscles differs greatlyin different kinds of animals; 

 it is greater in birds than in mammalia, and largest of all in the naked 

 amphibia. They are for themost part smaller in quadrupeds than in man; 

 in the elephant, however, they are larger, being Tr-yVatl^ of an inch, 

 which is the largest size yet observed in the blood-corpuscles of any 

 mammiferous animal ; the goat was long supposed to have the smallest, 

 viz., about T^iVn^^^ of ^^ inch; but Gulliver found them much smaller 

 in the Meminna and Napu musk-deer, in which animals they are less 

 than TirTjxroth of an inch. In birds they do not vary in size so much ; 

 from Gulliver's very elaborate tables of measurement it appears that 

 they range in length fi-om about o ^Vo^l^ t,o iTootli of an inch ; he 

 states that their breadth is usually a little more than half the length, 

 and their thickness about a third of the breadth or rather more. He 

 found a remarkable exception in the corpuscles of the snowy owl, which 

 measure y-Vo^'^ of an inch in length ; and arc only about a third of 

 this in breadth. In scaly reptiles they are from tjVo^^ ^o tttVo^Ii of 

 an inch in length ; in the naked amphibia they are much larger : thus, 

 in the frog they are xoW^^^ of an inch long, and TT^oirth broad ; in the 

 salamander they are larger still ; but the largest yet known a re found 

 in the protean reptiles. For example, in Proteus anguimis they are 

 ^f^yth of an inch in length, and y^-yth in breadth ; in the siren, which 

 is so much allied to the proteus in other respects, they measure -4^^th 

 of an inch in length, and ■f\o^^^ ^^ breadth, whilst in Amj>h//'ina 

 iridacfi/him they are as much as one-third larger than in the proteus. 

 In the skate and shark tribe the corpuscles resemble those of the 

 frog, in other fishes they are smaller. 



From what has been stated, it will be seen that the size of the blood- 

 corpuscles in animals generally is not proportionate to the size of the 

 body ; at the same time, as Gulliver remarks, " if we compare the 

 measurements made from a great number of diflFerent species of the 

 same order, it will be found that there is a closer connection between 

 the size of the animal and that of its blood-corpuscles than has been 

 generally supposed ; " and he has pointed out at least one example 

 of a very natural group of quadrupeds, the ruminants, in which there is 

 a gradation of the size of the corpuscles in relation to that of the 

 body. 



Structure. — The human red corpuscle is composed essentially of a 

 soft colourless stroma (tegumentary frame of Gulliver) of the same 

 shape and size as the corpuscle itself, throughout which is diffused a 

 semi-fluid coloured matter which may be readily separated from the 

 stroma by means of reagents. Some of these, such as water and acetic 

 acid, appear to act simply by dissolving out the coloured part, leaving 

 the stroma more or less swollen from imbibition of fluid. Others, such 

 as ether and chloroform and the salts of the biliary acids, cause the 

 discharge of the coloured matter into the surrounding fluid ; blood so 



