202 WARFIELD T. LONGCOPE AND GEOEGE M. MACKENZIE 



bed. In order to bring about this capillary dilatation, the capillaries 

 themselves must previously be in tone. They bring forward evidence thus 

 to show that the capillaries, far from being passive agents, take a very 

 active part in the circulation and are dilated by the direct toxic action 

 of histamin upon them. They finally discuss the relation of the condition 

 observed in histamin shock to that which may be present in anaphylactic 

 shock. Bearing upon this question are the important observations of 

 Krogh(&), who has shown that after stimulation of voluntary muscles, great 

 numbers of capillaries which in the resting muscle are practically invisible 

 become functionally active. In a single area of muscle not only is the 

 capillary bed greatly increased, but at times the diameters of the capillaries 

 already functioning are widened. Indeed, exactly this condition has been 

 observed to occur in the omentum of the rabbit following both the direct 

 application of histamin to the omentum and after the injection of this 

 substance intravenously. The dilatation of the capillaries of the omentum, 

 moreover, precedes by a measurable interval the drop in blood pressure and 

 therefore seems almost certainly to be the cause rather than the effect of 

 this phenomenon so characteristic of histamin shock. These observations 

 make it seem highly probable that an analogous condition may exist during 

 anaphylactic shock and indeed Weil(/i) has made the observation that 

 the injection of horse serum into the liver of a dog sensitized to this protein 

 results in a local engorgement of the organ in this region. 



The heart, however, does show a number of functional changes during 

 the reaction. Auer and Lewis first observed that auriculoventricular 

 dissociation occurred in guinea-pigs succumbing to anaphylactic shock, 

 resulting often in partial or even complete heart block, while more com- 

 plete study by Auer and Robinson (a) (I) showed that a variety of altera- 

 tions in the character and sequence of the heart beat were to be observed, 

 both in rabbits and in dogs which were subjected to anaphylactic shock. 

 Though several alterations in the electrocardiographic curves were noted, 

 the most important were the partial and complete blocks which occurred 

 in these animals. In the dog it is more customary to find merely a 

 lengthening of the P-R interval, but occasionally auriculoventricular dis- 

 sociation may be observed in this animal. Schulz(fr), too, has noted car- 

 diac irregularity in cats and has commented upon the auriculoventricular 

 dissociation that occurs. He likewise states that in these animals there is 

 an enormous engorgement of the right side of the heart and the pulmonary 

 artery, while the left side of the heart is practically empty. Together 

 with this the peripheral vessels are constricted. 



In connection with the phenomena of anaphylaxis in dogs an interest- 

 ing observation was made by Calvary, who by quantitative estimations, 

 found a great increase in the lymph flow independent of the changes in 

 blood pressure. 



That changes occur in the gastrointestinal tract is evidenced by many 



