350 THE DUCTLESS GLANDS 



According to Ho well, the responses become less and less 

 pronounced with each repeated injection. There is great 

 variation in the effects produced not only between different 

 species of animal, but even between different individuals of 

 the same species. 



It has been doubted whether the depressor action, seen with 

 injections subsequent to the first, is wholly due to a different 

 principle, though the evidence before us seems to the present 



FIG. 97. Effect upon the arterial pressure of intravenous injection of decoc- 

 tion of infundibular body. Cat. Morphine and curare. 



writer to be strongly in favour of such a view. Hoskins and 

 McPeek discuss the question, whether the pressor effect of 

 pituitary extract is due to adrenal stimulation, and come to a 

 negative conclusion. Experiments upon the isolated heart 

 of the frog and of mammals show that the slowing of the 

 heart-beat is due to a direct action upon the musculature of 

 the heart. Einis finds that the first effect of pituitary extract 

 upon the heart is a diminution of the frequency, this is followed 

 by an increase. 



2. Effects on the Vasomotor Reflexes 

 The facts that adrenin diminishes the. excitability of the 



