THE BLOOD. 



217 



FIG. 47. 



globules together, in any given quantity of blood, does not vary much 

 in different species; but in blood containing the smaller and more 

 abundant globules, their extent of surface, and probably their func- 

 tional activity, is greater than where they are larger and less numerous. 

 This will also apply to the inferior vertebrate animals, in which the 

 globules are often much larger and less numerous than in man. 



In birds, reptiles, and fish, comprising all the oviparous vertebrata as 

 well as some which are viviparous, the red globules are distinguished 

 by two marked characters of shape and structure, namely, an oval 

 form and the presence of a nucleus. The only known exceptions 

 are two species of fish, belonging to the family of the Lampreys, in 

 which the globules have a circular outline ; but here also they are 

 provided with a nucleus, and are therefore distinguishable from the 

 circular globules of mammalia. 



In the Batrachians, or naked 

 reptiles, the red globules pre- 

 sent the largest size and exhibit 

 most distinctly their structural 

 character. They are of a regu- 

 larly oval form, somewhat 

 thicker toward the edges and 

 thinner in the middle, the round 

 or oval, colorless, and granular 

 nucleus projecting slightly from 

 the lateral surface at its central 

 portion. In their reaction un- 

 der different physical and chem- 

 ical conditions, they resemble 

 the red globules of mammalians. 



In the frog the red globules 

 have a long diameter of 22 mmm., 

 or nearly three times that of the human globules; in Proteus anguinus, 

 the blind water-lizard of the Carniola grottoes, 58 mmm. ; in Meno- 

 branchus, a species inhabiting the northern lakes of the United States, 

 62.5 mmm. ; and in Amphiuma tridactylum, the great water-lizard of 

 Louisiana, according to Riddell, they are one-third larger than in 

 Proteus, or about 77 mmm. The following list gives the size of dif- 

 ferent globules of the oval form. 



LONG DIAMETER OF THE OVAL RED GLOBULES OF BIRDS, REPTILES, AXD Fisn r 

 in Micro-Millimetres. 



BLOOD-GLOBULES OF FROG. a. Red globule seen 

 edgewi.se. b. White globule. 



Fowl 

 Duck 

 Pigeon 

 Lizard 

 Alligator 

 Tortoise 

 Frog 



12.1 

 12.9 

 14.7 

 16.4 

 19.2 

 20.0 

 22.0 



Triton 



Proteus . 



Menobranchus 



Amphiuma 



Pen-h 



Carp 



Sturgeon . 



29.3 

 58.0 

 62.5 

 VT.O 

 12,0 

 13.1 

 13.4 



