456 STUDIES IN ADVANCED PHYSIOLOGY. 



SPECIAL FUNCTIONS OF THE BRAIN AND COED. 



It was pointed out that the function of the spinal cord is 

 two-fold. First, it serves as a tract along which sensory and 

 motor fibers run that connect the brain with the distant por- 

 tions of the body. Second, it consists of centers which are 

 concerned in the simple reflex actions. Thus, if a frog be 

 taken and its brain removed, and the toe of such a frog 

 pinched, the leg will be drawn up with almost as much 

 precision as in the case of an uninjured frog. A piece of 

 blotting paper soaked with an irritating solution, such as an 

 acid, placed on his skin will produce a series of the most 

 perfectly co-ordinated movements. If the foot be held firmly 

 and then pinched the frog at first tries to pull away the 

 injured foot and upon repeated failures to accomplish this it 

 will bring into play the foot on the other side to effect his 

 purpose. Here is a case in which the reflexes have become 

 complicated, have called in the opposite side of the spinal 

 cord, and yet are all so co-ordinated as to be directly pur- 

 posive. 



The question whether there are any automatic centers 

 in the spinal cord is still an open one, but the evidence 

 seems to show that it possesses reflex centers only. Instances 

 of impulses which seem to have originated in the spinal 

 cord have generally been traceable to outside influences for 

 their occasion. These outside influences are of course two. 

 First, sensations, carried by the sensory neurons directly to 

 it. In this case a reflex action arises without the interven- 

 tion of the brain. Second, motor impulses from the higher 

 centers of the brain. These higher impulses from the brain 

 calling into action these motor centers produce the ordinary 

 voluntary movements as we know them. 



While most of the reflexes of the spinal cord are natural, 

 that is, inherited, it is possible by training to establish 

 reflexes of a highly acquired character. Much of the quick 

 perception and delicate touch of an artist on most any kind 

 of an instrument is due to the establishment of fine reflexes 

 in his spinal cord. Such an artist is frequently able to re- 



