298 A MANUAL OF VETERINARY PHYSIOLOGY 



heart, bloodvessels and skeletal muscles generally, but with 

 certain marked differences. An extract of the posterior lobe 

 increases the tone of the heart-muscle, but not its rate of rhythm, 

 and though it constricts the arterioles generally, it causes 

 dilatation of the kidney. Schafer, whose work we have followed, 

 also points out that the pituitary contains a substance which 

 diminishes the force of the heart-beat, and inhibits the contrac- 

 tion of the arterioles, and that this, though overbalanced in the 

 artificial extract by the opposite effects, may, under physio- 

 logical conditions, be poured into the blood in such quantities 

 as the muscular system needs. One other possible function of 

 the pituitary may be referred to, and that is the influence of 

 extracts in producing a tonic effect on the nervous system, and 

 so assisting in maintaining not only the proper balance of the 

 circulation, but of tone, in the nerve centres generally. 



Nothing is known of the uses of the Pineal Body, an organ 

 regarded as the dorsal eye of a remote ancestor. 



