INFLUENCE OF THE NERVOUS SYSTEM. 175 



2. On modifying or suppressing the action of the heart, 

 we find that the blood still circulates in the arteries, and 

 flows into the veins, and, under these circumstances, an injec- 

 tion made upon a dying animal is most likely to succeed, the 

 peristaltism of the arteries making the blood penetrate the 

 finest nets of the capillaries. The weakening of the heart by 

 the administration of chloroform, of digitalis, or of alcohol, 

 in an animal in whom the cervical portion of the great sym- 

 pathetic is cut on one side, produces an excess of tempera- 

 ture, not of the side operated upon, but of the other side ; 

 the peristaltism of the arteries on this side alone being capa- 

 ble of producing a hypercemia, which may be called active, but 

 must not be confounded with the active dilatation of Schiff. 



8. By applying irritants to the peripheral extremity of the 

 sympathetic nerve when cut, we produce very different re- 

 sults, according as the excitations produced are tetanic, or 

 calculated to bring the peristaltism of the arterial tunics into 

 play. Thus, while powerful excitants produce anaemia of a 

 rabbit's ear, by producing a state of energetic and permanent 

 contraction, we find, on the contrary, that a slight ligature, 

 or the action of glycerine, or of nitrate of silver, etc., causes 

 considerable hyperaBmia, more important even than passive 

 hyperaBinia (neuro-paralytic) ; these results are, however, 

 still more striking if electricity be employed. While inter- 

 rupted currents (faradaic) paralyze the arteries (causing 

 ana3inia), we find that the continuous current (and only 

 when its direction is centrifugal) produces a very considerable 

 hyperaBinia in parts to which the sympathetic nerve, which is 

 thus excited, is distributed. Under similar circumstances, 

 microscopical examination of the interdigital membrane of a 

 frog reveals very decided peristaltism of the small vessels, 

 during the passage of the centrifugal continuous current. 



Thus certain excitants produce in the arteries slight or 

 clonic contractions, causing peristaltism and subsequent 

 hyperaBmia. Others cause tetanic contractions, bringing 

 on anaemia and chill. 



Differences of the same kind are observed in the manner 

 in which physiological excitants, the passions, for instance, 

 act on the vascularity of the skin in general, and on that of 

 the face in particular. Moleschott, who was attached to the 

 theory of vaso-motor paralyses, had already divided the pas- 

 sions into paralyzing and exciting passions / but when we 

 see, for instance, a slight anger cause redness of the face 

 (red anger) and a greater access of the same passion produce 



