300 



Comparative Animal Physiology 



f ABLE 52 (continued). LOCATION OF ABSORPTION BANDS OF VARIOUS 

 BLOOD PIGMENTS BY THEIR MAXIMA IN MILLIMICRA 



''or other pigment. 



by Svedberg and his associates with the ultracentrifuge.^^^ The sedimentation 

 constant of the protein in cm./sec./dyne of centrifugal force gives a measure 

 of molecular size. Sedimentation data for many hemoglobins are presented 

 in Table 53, together with such molecular weights as were calculated by Sved- 

 berg and Pedersen. The protein is similar in size in mammals, birds, and 

 fishes; it is slightly larger in amphibia and reptiles; and it is reduced by one- 

 half in cyclostomes, in which the hemoglobin molecule consists of two instead 

 of four units. In those invertebrates in which the hemoglobin (erythrocruorin 

 of Svedberg) is in solution in the plasma (except Chironomus}, the molecular 

 weight is greater than 1,000,000. The large size tends to conhne the molecules 

 to the circulatory system. In all those invertebrates in which the hemoglobin 

 occurs in cells, the molecular weight is less than that of vertebrate hemoglobin. 

 DiflFercnces in molecular size are due to differences in the proteins and in the 

 number of hemoglobin units per molecule. Svedberg"'^ suggested that the 



