252 



THE BLOOD 



In animals where the red globules are of comparatively smaller size 

 they are proportionally more numerous. It is estimated by Kolliker that 

 the entire volume or mass of all the red globules together, in any deter- 

 minate quantity of blood, does not vary much in different species ; and 

 that accordingly, in blood containing the smaller and more abundant 

 globules, the extent of their surface, and probably their functional 

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

 will apply also to the inferior groups of vertebrate animals, in which the 

 globules are often very much larger and at the same time less abundant 

 than in man. 



In the birds, reptiles, and fish, comprising all the oviparous verte- 

 brata, as well as some which are viviparous, the red globules are distin- 

 guished by two very marked characters of shape and structure : namely, 

 an oval form and the presence of a granular, colorless nucleus. The 

 only known exception is in 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 accordingly readily distin- 

 guishable from the circular globules of mammalia. 



It is among the Batrachians, or naked reptiles, that the red globules 

 present the largest size and exhibit most distinctly their structural 

 character. They are of a regularly oval form, their short diameter 



being between one-half and 

 three-quarters the long one, a 

 little thicker toward the edges 

 and thinner in the middle ; the 

 round or oval nucleus project- 

 ing slightly from the lateral 

 surface at its central portion 

 In their reactions toward dif- 

 ferent physical and chemical 

 agents, they resemble the red 

 blood-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- 

 branchns, an allied species inhabiting the northern lakes of the United 

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

 lizard of Louisiana, according to Dr. Riddell, the red globules are one- 

 third larger than in Proteus, or about 77 mmm. The following list 

 gives the size of different globules of the oval form. 



BLOOD-OLOBULKS OF FROG. a. Blood-glo 

 bule seen edgewise, b. White globule. 



