463 



CHAPTER VII. 



CIRCULATING AND RESPIRATORY SYSTEMS OF H2EMATOCRYA. 



81. Blood of Pishes.- -The red blood of Vertebrates owes 

 its colour to the albuminoid substance called ( haematosine, 

 existing in the discoid corpuscles called f blood-globules,' ' blood- 

 cells/ or ( blood-discs.' These float in the light straw-coloured 

 fluid called ( plasma,' which consists of water holding in solution 

 proteine principles, hydrocarbonates of the fatty nature, saccharine, 

 and saline matters. The watery solvent predominates in the 

 blood of Fishes and Batrachians. The f proteine' basis exists 

 under the combinations termed ' albumen ' and ( fibrin.' 



The blood-discs in Fishes are commonly of a full elliptic shape, 

 as in the Cod, fig. 8, y, and Skate, fig. 8, A, p. 4 : but in the 

 Lamprey and Ammocete they are nearly circular. In the Myxine, 

 however, they are elliptic, and some are fusiform. They present 

 the largest size in the Sharks, but are smaller in them in proportion 

 to the body, or mass of blood, than in Batrachia. 1 Besides the red 

 discs there are the larger white corpuscles in the blood of Fishes as 

 in that of higher Vertebrates, but in less proportion than in Sau- 

 rians, Birds, or Mammals. 



The comparison of main physiological importance between the 

 blood in different groups of Vertebrates, is that which relates to 

 the proportion of the organic matters contained in the water. 



Prevost and Dumas expressed the general results of this com- 

 parison of the blood of the cold-blooded classes in the following 



TABLE OF THE PROPORTION OF WATER, CLOT (BLOOD-DISCS AND FIBRIN), 



ALBUMEN, AND SALTS. 



1 See ccxxxix. torn. i. p. 89, for the dimensions, in fractions of a millemeter, of the 

 blood-discs of Fishes. 



2 CCLXV. p. 64. 



