6?>4 PHYSIOLOGY. 



Reflex Tonus of Spinal Cord. It cannot be denied that, in the 

 normal state, there is always a certain spinal tonus. That is to say, 

 an active state of the cord which is provoked by sensory excitations. 

 All of the muscles of the organism, striated as well as smooth, are 

 always in a stajte intermediate between relaxation and contraction. 

 This state of semiconstriction, of semiactivity, is governed by the 

 spinal cord. When the spinal cord is destroyed, immediately all of 

 the muscles of the body relax and their tonus ceases. 



Influence of the Blood. If a limb be separated from the rest of 

 the organism, and, consequently, receives no nutritive 'blood-current, 

 the function of the nerve nevertheless persists. 



By making Stenson's experiment (tying the abdominal aorta), 

 at the end of twenty minutes, or an hour at the most, it will be 

 found that sensibility and motility disappear in the abdominal mem- 

 bers. Though the deprivation of blood be complete, still there is 

 preservation of the nervous activity for some time. 



By using on man the ligature and then compressing the limb by 

 an Esmarch bandage interesting observations upon the influence of 

 anemia are made. During the first twenty minutes the arm is sen- 

 sitive and the cutaneous excitations are plainly perceived. Like- 

 wise the motor nerves can still command the movements of the 

 muscles. 



Soon, however, the sensibility becomes obtuse; the voluntary 

 movements take place only incompletely, without force, and slowly. 

 Next the sensibility disappears so completely that the strongest elec- 

 trical excitations are not felt. Because of the powerlessness of the 

 motor nerves, the limb feels limp and inert as if it were completely 

 paralyzed. 



This state of death of the nerves, from anaemia, contrasts with 

 the survival of the muscles. The nerve dies before the muscle, but 

 much later than the nervous centers. 



EXCITING EFFECTS OF ANEMIA. However it may be, anaemia, 

 which makes the functions of the nerve finally disappear, begins at 

 first by overexciting it. Thus, the first effects of anaemia are marked 

 by an increase of excitability. If it be a sensory member, anaemia 

 of it provokes extremely lively pains. 



Physicians have long been acquainted with painful anaemias. It 

 is anaemia, not absolute, "but relative, which is often the cause of 

 intense peripheral pains. Thus, in symmetrical gangrene of the 

 extremities (Raynaud's disease), which is characterized by nearly 

 complete cessation of the circulation in the affected areas, the pain 



