§ 5.421 BALANCE OF PHOSPHATES 249 



injected as Pituitrin into completely hypophysectomized toads 

 (Table 29; Shapiro and Zwarenstein, 1933). 



Mammalia. It has been claimed (e.g., Thomson and CoUip, 

 1932) that a hormone from the adrenal cortex can lower the level 

 of serum calcium in the rabbit; but these animals appear to be 

 particularly bad subjects for experiments on control of blood 

 calcium, owing to their variable responses. Conversely, however, 

 adrenalectomy raises the serum calcium in dogs. 



5.42 BALANCE OF PHOSPHATES 



There is a characteristic difference in the control of phosphates 

 in Crustacea and Vertebrata. In the former, the phosphate con- 

 centration in the blood changes in the same sense as does that of 

 calcium, and both are related to stages in moulting. In vertebrates 

 the changes in phosphates and calcium in the blood usually respond 

 to the same hormones, but do so in the opposite sense, phosphates 

 being decreased for instance when calcium is increased. 



The level of phosphates in the blood may, however, be a bad 

 indicator of the action of hormones on phosphate metabolism, 

 since the blood may be charged with phosphates as a result of 

 either protein catabolism or resorption of calcium phosphates from 

 vertebrate bone, and may be depleted either by excretion or by 

 protein synthesis in the tissues. 



5.421 Increase of phosphates in the blood 



Crustacea. Changes of phosphates in the blood are usually 

 similar to those of calcium ; but it appears that at least the threshold 

 values at which the controlling hormones become effective may be 

 different. For instance, in Panulirus (Travis, 1951), eyestalk 

 removal can decrease the phosphate content of the hepatopancreas 

 (and presumably increase the content of the blood) without 

 affecting the level of calcium; in most Decapoda, however, 

 eyestalk removal increases the level of both phosphates and calcium 

 in the blood. There is no direct evidence for the intervention of a 

 hormone from the Y-organ in the increase of phosphates in the 

 blood, as there is for calcium, nor that this is released from 

 inhibition by eyestalk removal (§ 5.411); but it may perhaps be 

 assumed to be active here also. 



